Filed Pursuant to Rule 424(b)(3)
Registration No. 333-226342

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

August 22, 2018

Dear Stockholder:

On June 18, 2018, First Connecticut Bancorp, Inc. (which we refer to as “First Connecticut”) entered into an Agreement and Plan of Merger (which we refer to as the “merger agreement”) with People’s United Financial, Inc. (which we refer to as “People’s United”). Under the merger agreement, First Connecticut will merge with and into People’s United, with People’s United as the surviving corporation, in a transaction that we refer to as the “merger”. Immediately following the merger or at such later time as People’s United may determine, First Connecticut’s wholly-owned subsidiary, Farmington Bank, will merge with and into People’s United’s wholly-owned subsidiary, People’s United Bank, National Association, with People’s United Bank, National Association as the surviving bank.

Under the terms and conditions of the merger agreement, each outstanding share of First Connecticut common stock, par value $0.01 per share (which we refer to as “First Connecticut common stock”) held immediately prior to the effective time of the merger, except for specified shares of First Connecticut common stock owned by First Connecticut or People’s United (which will be cancelled), will be converted into the right to receive 1.725 shares (which we refer to as the “merger consideration”) of People’s United common stock, par value $0.01 per share (which we refer to as “People’s United common stock”). The value of the merger consideration will depend on the market price of People’s United common stock on the effective date of the merger.

Shares of People’s United common stock are listed on the NASDAQ Global Select Market (which we refer to as “NASDAQ”) under the symbol “PBCT.” Shares of First Connecticut common stock are listed on NASDAQ under the symbol “FBNK.” Based on the closing price of People’s United common stock on NASDAQ on June 18, 2018, the last trading day before public announcement of the merger, the value of the per share merger consideration payable to holders of First Connecticut common stock would be $32.33. Based on the closing price of People’s United common stock on NASDAQ on August 20, 2018, the last practicable trading date before the date of the attached proxy statement/prospectus, the value of the per share merger consideration payable to holders of First Connecticut common stock would be $32.31. You should obtain current market quotations for both People’s United common stock and First Connecticut common stock. Based on the number of shares of First Connecticut common stock outstanding and the number of shares of First Connecticut common stock issuable pursuant to outstanding First Connecticut stock options, performance-based restricted stock unit awards and other equity awards, in each case as of August 20, 2018, the total number of shares of People’s United common stock expected to be issued in connection with the merger is approximately 32,505,257. In addition, based on the number of issued and outstanding shares of People’s United common stock and First Connecticut common stock on August 20, 2018, and based on the exchange ratio of 1.725, holders of shares of First Connecticut common stock as of immediately prior to the closing of the merger will hold, in the aggregate, approximately 8.5% of the issued and outstanding shares of People’s United common stock immediately following the closing of the merger (without giving effect to any People’s United common stock held by First Connecticut’s stockholders prior to the merger).

First Connecticut will hold a special meeting of its stockholders (which we refer to as the “special meeting”) in connection with the merger. First Connecticut’s stockholders will be asked to vote to approve the merger, as described in the attached proxy statement/prospectus. The merger cannot be completed unless, among other things, the holders of at least two-thirds of the outstanding shares of First Connecticut common stock vote to approve the merger. At the special meeting, First Connecticut’s stockholders will also be asked to vote on (i) the non-binding, advisory proposal to approve the compensation that certain named executive officers of First Connecticut may receive that is based on or otherwise relates to the merger and (ii) a proposal to approve the adjournment of the special meeting, if necessary or appropriate, to solicit additional proxies in favor of the merger proposal. The special meeting of stockholders of First Connecticut will be held at Farmington Club, 162 Town Farm Road, Farmington, CT 06032 on Tuesday, September 25, 2018 at 10:00 a.m., Eastern Time. First Connecticut’s board of directors has unanimously approved and adopted the merger agreement and the transactions contemplated thereby and recommends that you vote “FOR” the approval of the merger, and “FOR” the other matters to be considered at the special meeting.

The attached proxy statement/prospectus, which serves as the proxy statement for the special meeting of the stockholders of First Connecticut and the prospectus for the shares of People’s United common stock to be issued in the merger, includes detailed information about the special meeting, the merger and the documents related to the merger. We urge you to read the entire proxy statement/prospectus carefully, including the discussion of the risks related to the merger and owning People’s United common stock after the merger in the section titled “Risk Factors” beginning on page 24. You can also obtain information about First Connecticut and People’s United from documents that have been filed with the Securities and Exchange Commission that are incorporated in this proxy statement/prospectus by reference.

Your vote is very important. To ensure your representation at the special meeting, please promptly complete sign, date and return the enclosed proxy card to First Connecticut in the enclosed postage-paid envelope or by submitting a proxy through the Internet or by telephone as described on the enclosed instructions. If you hold your shares or depositary shares in “street name,” you should instruct your broker, bank or other nominee how to vote in accordance with the voting instruction form you receive from your broker, bank or other nominee.

Sincerely,

John J. Patrick, Jr.

Chairman, President and Chief Executive Officer

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in the merger or passed upon the adequacy or accuracy of this proxy statement/prospectus. Any representation to the contrary is a criminal offense.

The shares of People’s United common stock to be issued in connection with the merger are not savings accounts, deposits or other obligations of any bank or savings association and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

This proxy statement/prospectus is dated August 22, 2018, and is first being mailed to First Connecticut’s stockholders on or about August 22, 2018.

ADDITIONAL INFORMATION

The accompanying proxy statement/prospectus incorporates by reference important business and financial information about People’s United Financial, Inc. (which we refer to as “People’s United”) and First Connecticut Bancorp, Inc. (which we refer to as “First Connecticut”) from documents filed with the Securities and Exchange Commission (which we refer to as the “SEC”) that are not included in or delivered with the proxy statement/prospectus. You can obtain any of the documents filed with or furnished to the SEC by People’s United or First Connecticut at no cost from the SEC’s website at http://www.sec.gov. You will also be able to obtain these documents, free of charge, from People’s United at www.peoples.com (“Investor Relations” tab under the heading “Financial Information” and under the subheading “Regulatory Filings”) or from First Connecticut at www.firstconnecticutbancorp.com (“Documents” tab under the heading “SEC Filings”). Additionally, you may also request copies of these documents, including documents incorporated by reference in the proxy statement/prospectus, at no cost upon written or oral request by contacting the appropriate company at the following addresses and telephone numbers:

You will not be charged for any of these documents that you request. To obtain timely delivery of these documents, you must request them no later than five business days before the date of the special meeting. This means that First Connecticut’s stockholders requesting documents must do so by September 18, 2018, in order to receive them before the special meeting.

For a more detailed description of the information incorporated by reference in the accompanying proxy statement/prospectus and how you may obtain it, see “Where You Can Find More Information,” beginning on page 104 of the accompanying proxy statement/prospectus. The accompanying proxy statement/prospectus provides a detailed description of the merger and the merger agreement. We urge you to read the accompanying proxy statement/prospectus, including any documents incorporated by reference into the accompanying proxy statement/prospectus, and its annexes carefully and in their entirety.

If you have any questions concerning the merger, the other matters to be considered at the special meeting or the accompanying proxy statement/prospectus or need assistance voting your shares of First Connecticut common stock, please contact First Connecticut’s proxy solicitor at the address or telephone number listed below:

Morrow Sodali LLC

470 West Avenue

Stamford, CT 06902

Please do not send your stock certificates at this time. You will be sent separate instructions regarding the surrender of your stock certificates.

You should rely only on the information contained in, or incorporated by reference into, the proxy statement/prospectus. No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, the proxy statement/prospectus. The proxy statement/prospectus is dated August 22, 2018, and you should assume that the information in the proxy statement/prospectus is accurate only as of such date unless information specifically indicates that another date applies.

The proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction in which or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction.

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

August 22, 2018

To the stockholders of First Connecticut Bancorp, Inc.:

Notice is hereby given that a special meeting of stockholders (which we refer to as the “special meeting”) of First Connecticut Bancorp, Inc., a Maryland corporation (which we refer to as “First Connecticut”), will be held at Farmington Club, 162 Town Farm Road, Farmington, CT 06032 on Tuesday, September 25, 2018 at 10:00 a.m., Eastern Time, for the purpose of considering and voting upon the following matters:

First Connecticut will transact no other business at the special meeting except for business properly brought before the special meeting or any adjournment or postponement thereof.

First Connecticut’s board of directors has fixed the close of business on August 20, 2018 as the record date for determination of stockholders entitled to notice of and to vote at the special meeting, and only stockholders of record on said date will be entitled to receive notice of and to vote at said meeting.

The affirmative vote of the holders of at least two-thirds of the outstanding shares of First Connecticut common stock is required to approve the merger proposal. The affirmative vote of the holders of at least a majority of the votes cast at the special meeting is required to approve each of the compensation proposal and the adjournment proposal.

First Connecticut’s board of directors has unanimously approved and adopted the merger agreement and the transactions contemplated thereby and recommends that you vote “FOR” the merger proposal, “FOR” the compensation proposal and “FOR” the adjournment proposal.

Your vote is very important. Whether or not you plan to attend the special meeting, please take the time to vote by completing, signing, dating and returning the enclosed proxy card to First Connecticut in the enclosed postage-paid envelope or by submitting a proxy through the Internet or by telephone as described on the enclosed instructions as soon as possible to make sure your shares of First Connecticut common stock are represented at the special meeting. If you submit a properly signed proxy card without indicating how you want to vote, your proxy will be counted as a vote “FOR” the merger proposal, “FOR” the compensation proposal and “FOR” the adjournment proposal. The failure to vote by not submitting your proxy or not attending the special meeting and voting in person will have the same effect as a vote against the merger proposal. Submitting a proxy now will NOT prevent you from being able to vote in person at the special meeting. If you hold your shares of First Connecticut common stock in “street name,” through a bank, broker or other nominee, you should instruct your bank, broker or other nominee how to vote in accordance with the voting instruction form you receive from your bank, broker or other nominee.

By Order of the Board of Directors

Jennifer H. Daukas

Corporate Secretary

Table of Contents

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QUESTIONS AND ANSWERS ABOUT THE MERGER AND THE SPECIAL MEETING

The following questions and answers are intended to address briefly some commonly asked questions regarding the merger and the special meeting. These questions and answers may not address all questions that may be important to you as a stockholder. To better understand these matters, and for a description of the legal terms governing the merger, you should carefully read this entire proxy statement/prospectus, including the annexes, as well as the documents that have been incorporated by reference in this proxy statement/prospectus.

This proxy statement/prospectus contains important information about the merger, the merger agreement, the special meeting of First Connecticut’s stockholders and other related matters, and you should read it carefully. The enclosed voting materials for the special meeting allow you to vote your shares of First Connecticut common stock, par value $0.01 per share (which we refer to as “First Connecticut common stock”) without attending the special meeting in person. Your vote is important, and we encourage you to submit your proxy as soon as possible.

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Compensation proposal:

Adjournment proposal:

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First Connecticut’s stockholders must approve the merger proposal in order for the merger to occur. First Connecticut’s stockholders are not, however, required to approve the compensation proposal or the adjournment proposal in order for the merger to occur. If First Connecticut’s stockholders fail to approve the compensation proposal or the adjournment proposal, but approve the merger proposal, the merger may nonetheless occur.

If you intend to submit your proxy through the Internet or by telephone, you must do so by 11:59 P.M. Eastern Time on September 24, 2018, the day before the special meeting. If you intend to submit your proxy by mail, your completed proxy card must be received prior to the special meeting.

If you hold your shares of First Connecticut common stock in “street name” through a bank, broker or other nominee, you must direct your bank, broker or other nominee how to vote in accordance with the instructions you have received from your bank, broker or other nominee.

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You should send any written notice of revocation or duly executed new proxy, as the case may be, to First Connecticut at the following address:

First Connecticut Bancorp, Inc.

One Farm Glen Boulevard

Farmington, Connecticut 06032

Attn: Jennifer H. Daukas, Corporate Secretary

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If you hold your shares of First Connecticut common stock in “street name” through a bank, broker or other nominee, you must contact your record holder to change your vote.

Q: What happens if I sell my shares of First Connecticut common stock after the record date but before the special meeting?

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RISK FACTORS

In addition to the general investment risks and the other information contained in or incorporated by reference into this proxy statement/prospectus, including the matters addressed under the caption “Information Regarding Forward-Looking Statements,” beginning on page 32, you should carefully consider the following risk factors in deciding how to vote on the proposals presented in this proxy statement/prospectus. You should also consider the other information in this proxy statement/prospectus and the other documents incorporated by reference in this proxy statement/prospectus. For more information, see “Where You Can Find More Information,” beginning on page 104.

Risks Related to the Merger and People’s United’s Business upon Completion of the Merger

Because the market price of People’s United common stock will fluctuate, First Connecticut’s stockholders cannot be certain of the market value of the merger consideration they will receive.

Upon completion of the merger, each outstanding share of First Connecticut common stock held immediately prior to the effective time of the merger, except for specified shares of First Connecticut common stock owned by First Connecticut or People’s United (which will be cancelled), will be converted into the right to receive 1.725 shares of People’s United common stock. The market value of the People’s United common stock to be issued in the merger will depend upon the market price of People’s United common stock and of First Connecticut common stock. The market value of People’s United common stock and First Connecticut common stock at the effective time of the merger may vary significantly from their respective values on the date the merger was announced or at other dates, including on the date that this proxy statement/prospectus was mailed to First Connecticut’s stockholders and on the date of the First Connecticut special meeting. There will be no adjustment to the merger consideration for changes in the market price of either shares of People’s United common stock or First Connecticut common stock.

The market price of People’s United common stock and First Connecticut common stock may result from a variety of factors, including, but not limited to, changes in sentiment in the market regarding People’s United’s and First Connecticut’s operations or business prospects, including market sentiment regarding People’s United’s and/or First Connecticut’s entry into the merger agreement. These risks may also be affected by:

Many of these factors are outside the control of People’s United and First Connecticut. Accordingly, at the time of the First Connecticut special meeting, First Connecticut’s stockholders will not necessarily know or be able to calculate the value of the merger consideration they would be entitled to receive upon completion of the merger. You should obtain current market quotations for both People’s United common stock and First Connecticut common stock.

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The market price of People’s United common stock after the merger may be affected by factors different from those affecting the shares of People’s United or First Connecticut currently.

The businesses of People’s United and First Connecticut differ, and accordingly, the results of operations of the combined company and the market price of the shares of People’s United’s common stock after the completion of the merger may be affected by factors different from those currently affecting the independent results of operations and market prices of common stock of each of People’s United and First Connecticut. For a discussion of the businesses of People’s United and First Connecticut and of certain factors to consider in connection with those businesses, see the documents incorporated by reference in this proxy statement/prospectus and referred to under “Where You Can Find More Information,” beginning on page 104.

The success of the merger and integration of People’s United and First Connecticut will depend on a number of uncertain factors.

The success of the merger will depend on a number of factors, including:

Integrating the acquired branches will be an operation of substantial size and expense and may be affected by general market and economic conditions or government actions affecting the financial industry generally. Integration efforts will also likely divert People’s United’s management’s attention and resources. No assurance can be given that People’s United will be able to integrate the acquired branches successfully. Additionally, no assurance can be given that the operation of the acquired branches will not adversely affect People’s United’s existing profitability, that People’s United will be able to achieve results in the future similar to those achieved by its existing banking business or that People’s United will be able to manage any growth resulting from the merger effectively.

Regulatory Approvals May Not Be Received, May Take Longer than Expected or May Impose Conditions that Are Not Presently Anticipated or Cannot Be Met

Before the transactions contemplated in the merger agreement can be completed, various approvals must be obtained from the bank regulatory and other governmental authorities. In deciding whether to grant these approvals, the relevant governmental entities will consider a variety of factors, including the regulatory standing of each of the parties, the effect of the merger on competition, and the factors described in the section of this proxy statement/prospectus entitled “The Merger—Regulatory Approvals Required for the Merger” beginning on page 67. An adverse development in either party’s regulatory standing or other factors could result in an inability to obtain one or more of the required regulatory approvals or delay receipt of required approvals. The Federal Reserve Board has stated that if supervisory issues arise during processing of an application for approval of a merger transaction, a banking organization will be expected to withdraw its application pending resolution of such supervisory concerns. No assurance can be given that the OCC would not also require a similar withdrawal of an application if supervisory issues arise during processing of an application for approval of a bank merger

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transaction. Accordingly, if there is an adverse development in either party’s regulatory standing, People’s United or People’s United Bank may be required to withdraw its application for approval of the proposed merger and bank merger, as applicable, and, if possible, resubmit such application after the applicable supervisory concerns have been resolved.

The terms of the approvals that are granted may impose conditions, limitations, obligations or costs, or place restrictions on the conduct of the combined company’s business or require changes to the terms of the transactions contemplated by the merger agreement. There can be no assurance that regulators will not impose any such conditions, limitations, obligations or restrictions and that such conditions, limitations, obligations or restrictions will not have the effect of delaying the completion of any of the transactions contemplated by the merger agreement, imposing additional material costs on or materially limiting the revenues of the combined company following the merger or otherwise reduce the anticipated benefits of the merger if the merger were consummated successfully within the expected timeframe. Nor can there be any assurance that any such conditions, terms, obligations or restrictions will not result in the delay or abandonment of the merger. Additionally, the completion of the merger is conditioned on the absence of certain orders, injunctions or decrees by any court or regulatory agency of competent jurisdiction that would prohibit or make illegal the completion of any of the transactions contemplated by the merger agreement.

People’s United and First Connecticut believe that the proposed transactions should not raise significant regulatory concerns and that People’s United will be able to obtain all requisite regulatory approvals in a timely manner. However, the processing time for obtaining regulatory approvals for mergers of banking institutions, particularly for larger institutions, has increased since the financial crisis of 2007-2008. In addition, despite the parties’ commitments to use their reasonable best efforts to comply with conditions imposed by regulatory entities, under the terms of the merger agreement, People’s United will not be required and First Connecticut will not be permitted to take actions that would reasonably be expected to have a material adverse effect on People’s United and its subsidiaries, taken as a whole, after giving effect to the merger (measured on a scale relative to First Connecticut and its subsidiaries, taken as a whole). See “The Merger—Regulatory Approvals Required for the Merger” beginning on page 67.

Combining People’s United and First Connecticut may be more difficult, costly or time consuming than expected and the anticipated benefits and cost savings of the merger may not be realized.

People’s United and First Connecticut have operated and, until the completion of the merger, will continue to operate, independently. The success of the merger, including anticipated benefits and cost savings, will depend, in part, on People’s United’s ability to successfully combine and integrate the businesses of People’s United and First Connecticut in a manner that permits growth opportunities and does not materially disrupt existing customer relations nor result in decreased revenues due to loss of customers. It is possible that the integration process could result in the loss of key employees, the disruption of either company’s ongoing businesses or inconsistencies in standards, controls, procedures and policies that adversely affect the combined company’s ability to maintain relationships with clients, customers, depositors and employees or to achieve the anticipated benefits and cost savings of the merger. The loss of key employees could adversely affect People’s United’s ability to successfully conduct its business, which could have an adverse effect on People’s United’s financial results and the value of its common stock. People’s United may also encounter unexpected difficulties or costs during the integration that could adversely affect its earnings and financial condition, perhaps materially. If People’s United experiences difficulties with the integration process and attendant systems conversion, the anticipated benefits of the merger may not be realized fully or at all or may take longer to realize than expected. As with any merger of financial institutions, there also may be business disruptions that cause People’s United and/or First Connecticut to lose customers or cause customers to remove their accounts from People’s United and/or First Connecticut and move their business to competing financial institutions. Integration efforts between the two companies may also divert management’s attention and resources. These integration matters could have an adverse effect on each of People’s United and First Connecticut during this transition period and for an undetermined period after completion of the merger on the combined company. In addition, the actual cost savings of the merger could be less than anticipated or could take longer to anticipate than expected.

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The combined company may be unable to retain People’s United and/or First Connecticut personnel successfully after the merger is completed.

The success of the merger will depend in part on the combined company’s ability to retain the talents and dedication of key employees currently employed by People’s United and First Connecticut. It is possible that these employees may decide not to remain with People’s United or First Connecticut, as applicable, while the merger is pending or with the combined company after the merger is consummated. If key employees terminate their employment or if an insufficient number of employees is retained to maintain effective operations, the combined company’s business activities may be adversely affected, and management’s attention may be diverted from successfully integrating First Connecticut to hiring suitable replacements, all of which may cause the combined company’s business to suffer. In addition, People’s United and First Connecticut may not be able to locate suitable replacements for any key employees who leave either company or to offer employment to potential replacements on reasonable terms.

The merger agreement limits First Connecticut’s ability to pursue alternatives to the merger.

The merger agreement contains provisions that make it more difficult for First Connecticut to sell its business to a party other than People’s United. These provisions include a general prohibition on First Connecticut’s solicitation of, or, subject to certain exceptions relating to the exercise of fiduciary duties by First Connecticut’s board of directors, entering into discussions with any third party regarding any acquisition proposal or offer for a competing transaction, the requirement that First Connecticut pay the $22.5 million termination fee if the merger agreement is terminated in certain circumstances and the requirement that First Connecticut submit the merger proposal to a vote of First Connecticut’s stockholders even if First Connecticut’s board of directors changes its recommendation in favor of the merger proposal in a manner adverse to People’s United. For more information, see “The Merger Agreement—Agreement Not to Solicit Other Offers,” “The Merger Agreement—Termination Fee” and “The Merger Agreement—Stockholder Meeting of First Connecticut and Recommendation of First Connecticut’s Board of Directors,” beginning on pages 83, 86 and 83, respectively.

These provisions might discourage a third party that might have an interest in acquiring all or a significant part of First Connecticut from considering or proposing that acquisition, even if that party were prepared to pay consideration with a higher per share value than the proposed merger consideration. Furthermore, a potential competing acquiror may propose to pay a lower per share price to First Connecticut’s stockholders than it might otherwise have proposed to pay because of First Connecticut’s obligation, in connection with termination of the merger agreement under certain circumstances, to pay People’s United the termination fee.

The merger agreement may be terminated in accordance with its terms, and the merger may not be completed.

The merger agreement is subject to a number of conditions, which must be fulfilled in order to complete the merger. Those conditions include: (i) the approval of the merger proposal by the requisite vote of First Connecticut’s stockholders; (ii) the authorization for listing on NASDAQ of the shares of People’s United common stock to be issued pursuant to the merger; (iii) the receipt of all required regulatory approvals which are necessary to consummate the transactions contemplated by the merger agreement and the expiration of all statutory waiting periods without the imposition of a materially burdensome regulatory condition; (iv) the effectiveness of the registration statement of which this proxy statement/prospectus is a part with respect to the People’s United common stock to be issued upon the consummation of the merger; (v) the absence of any order, injunction or other legal restraint preventing the completion of the merger or making the completion of the merger illegal; (vi) subject to certain exceptions, the accuracy of the representations and warranties of each of People’s United and First Connecticut; (vii) performance in all material respects by each of People’s United and First Connecticut of its respective obligations under the merger agreement; and (viii) the receipt by each of People’s United and First Connecticut of an opinion from its respective counsel to the effect that the merger will be treated as a “reorganization” within the meaning of Section 368(a) of the Code. These conditions to the closing of the merger may not be fulfilled in a timely manner or at all, and, accordingly, the merger may not be completed.

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In addition, the parties may mutually decide to terminate the agreement at any time, before or after the approval of the merger proposal by the First Connecticut stockholders, or People’s United or First Connecticut may choose to terminate the merger agreement in certain other circumstances. For a more complete discussion of the circumstances under which the merger agreement could be terminated, see “The Merger Agreement—Termination of the Merger Agreement,” beginning on page 85.

Lawsuits challenging the merger may be filed against First Connecticut and People’s United, and an adverse judgment in any such lawsuit or any future similar lawsuits may prevent the merger from becoming effective or from becoming effective within the expected timeframe.

Stockholders of First Connecticut may file lawsuits against First Connecticut, People’s United and/or the directors and officers of either company in connection with the merger. For more information, see “The Merger—Litigation Related to the Merger,” beginning on page 71. One of the conditions to the closing of the merger is that no order, injunction or decree issued by any court or agency of competent jurisdiction or other legal restraint or prohibition that prevents the consummation of the merger or any of the other transactions contemplated by the merger agreement be in effect. If any plaintiff were successful in obtaining an injunction prohibiting First Connecticut or People’s United defendants from completing the merger on the agreed upon terms, then such injunction may prevent the merger from becoming effective or from becoming effective within the expected timeframe and could result in significant costs to First Connecticut and/or People’s United, including any cost associated with the indemnification of directors and officers. The defense or settlement of any lawsuit or claim that remains unresolved at the time the merger is completed may adversely affect People’s United’s business, financial condition, results of operations and cash flow.

First Connecticut’s stockholders will have a reduced ownership and voting interest after the merger and will exercise less influence over management of the combined organization.

First Connecticut’s stockholders currently have the right to vote in the election of First Connecticut’s board of directors and on other matters affecting First Connecticut requiring stockholder approval under Maryland law and First Connecticut’s charter and bylaws. Upon the completion of the merger, each of First Connecticut’s stockholders that receives shares of People’s United common stock will become a stockholder of People’s United with a percentage ownership of the combined organization that is much smaller than the stockholder’s percentage ownership of First Connecticut. Based on the number of shares outstanding on August 20, 2018, and based on the exchange ratio of 1.725, it is expected that First Connecticut’s former stockholders as a group will receive shares in the merger constituting approximately 8.5% of the outstanding shares of People’s United common stock immediately after the merger. Because of this, First Connecticut’s stockholders as a group will have significantly less influence on the management and policies of People’s United than they now have on the management and policies of First Connecticut.

First Connecticut’s stockholders will not have dissenters’ or appraisal rights in the merger.

Dissenters’ and appraisal rights are statutory rights that, if applicable under law, enable stockholders to dissent from an extraordinary transaction, such as a merger, and to demand that the corporation pay the fair value for their shares as determined by a court in a judicial proceeding instead of receiving the consideration offered to stockholders in connection with the extraordinary transaction. Under the MGCL, the charter of a Maryland corporation may eliminate appraisal rights. First Connecticut’s articles of incorporation provides that stockholders are not entitled to exercise any appraisal rights or dissenters’ rights in connection with a transaction such as a merger. Accordingly, First Connecticut stockholders will not be entitled to assert any appraisal or dissenters’ rights with respect to their shares of First Connecticut common stock in connection with the merger.

Certain of First Connecticut’s directors and executive officers have interests in the merger that may be different from, or in addition to, the interests of First Connecticut’s stockholders generally.

In considering the information contained in this proxy statement/prospectus, you should be aware that some of First Connecticut’s executive officers and directors have interests in the merger that may be different from, or in

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addition to, the interests of First Connecticut’s stockholders generally. These interests include the vesting in full of certain outstanding First Connecticut equity compensation awards and rights to continued indemnification and insurance coverage by People’s United after the merger for acts or omissions occurring before the merger. These interests and arrangements may create potential conflicts of interest. First Connecticut’s board of directors was aware of these interests and considered these interests, among other matters, when making its decision to approve the merger and in recommending that First Connecticut’s stockholders vote in favor of the merger proposal.

For a more complete discussion of these interests, see “The Merger—Interests of First Connecticut’s Directors and Executive Officers in the Merger,” beginning on page 59.

The fairness opinion delivered by First Connecticut’s financial advisor to First Connecticut’s board of directors prior to the execution of the merger agreement will not reflect changes in circumstances subsequent to the date of the fairness opinion.

Piper, First Connecticut’s financial advisor in connection with the merger, delivered its fairness opinion to First Connecticut’s board of directors on June 18, 2018. The opinion of Piper speaks only as of such date and does not reflect changes that may occur or may have occurred after the date of the opinion, including changes to the operations and prospects of People’s United or First Connecticut, changes in general market and economic conditions or regulatory or other factors. Any such changes may materially alter or affect the relative values of People’s United and First Connecticut.

The merger is subject to the receipt of consents and approvals from governmental entities that may not be received, delay the date of completion of the merger or impose conditions that could have an adverse effect on People’s United.

Before the merger and the bank merger may be completed, various approvals or consents must be obtained from governmental authorities. Satisfying the requirements of these governmental entities may delay the date of completion of the merger. In addition, these governmental entities may include conditions on the completion of the merger or require changes to the terms of the merger. While People’s United and First Connecticut do not currently expect that any such conditions or changes would result in a material adverse effect on People’s United, there can be no assurance that they will not, and such conditions or changes could have the effect of delaying completion of the merger or imposing additional costs on or limiting the revenues of People’s United following the merger, any of which might have a material adverse effect on People’s United following the merger.

First Connecticut and People’s United will be subject to business uncertainties and contractual restrictions while the merger is pending.

Uncertainty about the effect of the merger on employees and customers may have an adverse effect on First Connecticut or People’s United. These uncertainties may impair First Connecticut’s or People’s United’s ability to attract, retain and motivate key personnel until the merger is completed and could cause customers and others that deal with First Connecticut or People’s United to seek to change existing business relationships with First Connecticut or People’s United. Retention of certain employees by First Connecticut or People’s United may be challenging while the merger is pending, as certain employees may experience uncertainty about their future roles with the combined company. If key employees depart because of issues relating to the uncertainty and difficulty of integration or a desire not to remain with First Connecticut or People’s United, First Connecticut’s business or People’s United’s business could be harmed. In addition, subject to certain exceptions, First Connecticut has agreed to operate its business in the ordinary course prior to closing, and People’s United is also subject to certain restrictions on the conduct of its business prior to closing. For more information, see “The Merger Agreement—Covenants and Agreements,” beginning on page 77.

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Failure to complete the merger could negatively impact the stock prices, future businesses and financial results of People’s United and First Connecticut.

If the merger is not completed, the ongoing businesses of People’s United and First Connecticut may be adversely affected, and People’s United and First Connecticut will be subject to several risks, including the following:

In addition, if the merger is not completed, People’s United and/or First Connecticut may experience negative reactions from the financial markets and from their respective customers and employees. For example, People’s United’s and First Connecticut’s businesses may be impacted adversely by the failure to pursue other beneficial opportunities due to the focus of management on the merger, without realizing any of the anticipated benefits of completing the merger. The market price of People’s United’s or First Connecticut’s common stock could decline to the extent that the current market prices reflect a market assumption that the merger will be completed. People’s United and/or First Connecticut also could be subject to litigation related to any failure to complete the merger or to proceedings commenced against People’s United or First Connecticut to perform their respective obligations under the merger agreement. If the merger is not completed, People’s United and First Connecticut cannot assure their respective stockholders that the risks described above will not materialize and will not materially affect the business, financial results and stock prices of People’s United and/or First Connecticut.

If the merger is not completed, People’s United and First Connecticut will have incurred substantial expenses without realizing the expected benefits of the merger.

Each of People’s United and First Connecticut has incurred and will incur substantial expenses in connection with the negotiation and completion of the transactions contemplated by the merger agreement, as well as the costs and expenses of filing, printing and mailing this proxy statement/prospectus and all filing and other fees paid to the SEC in connection with the merger. If the merger is not completed, People’s United and First Connecticut would have to recognize these expenses without realizing the expected benefits of the merger.

The shares of People’s United common stock to be received by First Connecticut’s stockholders as a result of the merger will have different rights from shares of First Connecticut common stock.

Following completion of the merger, First Connecticut’s stockholders will become stockholders of People’s United, and their rights as stockholders will be governed by the Delaware General Corporation Law (which we refer to as the “DGCL”) and People’s United’s charter and bylaws. There will be important differences between your current rights as a stockholder of First Connecticut and the rights to which you will be entitled as a stockholder of People’s United. For a discussion of the different rights associated with People’s United common stock and First Connecticut common stock, see “Comparison of Stockholder Rights,” beginning on page 90.

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Risks Relating to People’s United Business

You should read and consider risk factors specific to People’s United’s business that will also affect the combined company after the merger. These risks are described in the sections entitled “Risk Factors” in People’s United’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 and in other documents incorporated by reference into this proxy statement/prospectus. For more information, see “Where You Can Find More Information,” beginning on page 104.

Risks Relating to First Connecticut’s Business

You should read and consider risk factors specific to First Connecticut’s business that will also affect the combined company after the merger. These risks are described in the sections entitled “Risk Factors” in First Connecticut’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 and in other documents incorporated by reference into this proxy statement/prospectus. For more information, see “Where You Can Find More Information,” beginning on page 104.

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INFORMATION REGARDING FORWARD-LOOKING STATEMENTS

This proxy statement/prospectus, including information included or incorporated by reference in this proxy statement/prospectus, may contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include, but are not limited to, statements about the benefits of the merger between People’s United and First Connecticut, including People’s United’s and/or First Connecticut’s expectations or predictions of future financial or business performance or conditions; statements about People’s United’s and First Connecticut’s plans, objectives, expectations and intentions with respect to future operations, products and services; and other statements identified by words such as “believe,” “expect,” “anticipate,” “intend,” “target,” “estimate,” “continue,” “positions,” “plan,” “predict,” “project,” “forecast,” “guidance,” “goal,” “objective,” “prospects,” “possible” or “potential,” by future conditional verbs such as “assume,” “will,” “would,” “should,” “could” or “may,” or by variations of such words or by similar expressions. These forward-looking statements are subject to numerous assumptions, risks and uncertainties, which change over time, are difficult to predict and are generally beyond the control of either company. Forward-looking statements speak only as of the date they are made, and People’s United and First Connecticut assume no duty to update forward-looking statements. Actual results may differ materially from current projections.

In addition to factors previously disclosed in People’s United’s and First Connecticut’s reports filed with the SEC and those identified elsewhere in this proxy statement/prospectus, the following factors, among others, could cause actual results to differ materially from forward-looking statements or historical performance:

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Additional factors that could cause People’s United’s and First Connecticut’s results to differ materially from those described in the forward-looking statements can be found in People’s United’s and First Connecticut’s filings with the SEC, including People’s United’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 and First Connecticut’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017.

You are cautioned not to place undue reliance on the forward-looking statements, which speak only as of the date of this proxy statement/prospectus or the date of the applicable document incorporated by reference in this proxy statement/prospectus. All subsequent written and oral forward-looking statements concerning the merger or other matters addressed in this proxy statement/prospectus and attributable to People’s United or First Connecticut or any person acting on their behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. Except to the extent required by applicable law or regulation, People’s United and First Connecticut undertake no obligation to update these forward-looking statements to reflect facts, assumptions, events or circumstances that occur after the date on which such forward-looking statement was made.

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THE SPECIAL MEETING OF FIRST CONNECTICUT’S STOCKHOLDERS

This section contains information for First Connecticut’s stockholders about the special meeting that First Connecticut has called to allow its stockholders to consider and vote on the merger proposal and other matters as described below. On or about August 22, 2018, this proxy statement/prospectus was mailed to holders of First Connecticut common stock entitled to vote at the special meeting. This proxy statement/prospectus is accompanied by a notice of the special meeting of First Connecticut’s stockholders and a form of proxy card that First Connecticut’s board of directors is soliciting for use at the special meeting and at any adjournments or postponements thereof.

Date, Time and Place of the Special Meeting

The special meeting of stockholders of First Connecticut will be held at Farmington Club, 162 Town Farm Road, Farmington, CT 06032 on Tuesday, September 25, 2018 at 10:00 a.m., Eastern Time.

Purpose of the Special Meeting

At the special meeting, First Connecticut’s stockholders as of the record date will be asked to consider and vote on the following proposals:

Recommendation of First Connecticut’s Board of Directors

First Connecticut’s board of directors has unanimously approved and adopted the merger agreement and the transactions contemplated thereby and recommends that you vote “FOR” the merger proposal, “FOR” the compensation proposal and “FOR” the adjournment proposal.

Record Date, Outstanding Shares, Shares Entitled to Vote and Quorum

First Connecticut’s board of directors has fixed the close of business on August 20, 2018 as the record date for determining the holders of First Connecticut common stock entitled to receive notice of and to vote at the special meeting.

As of the record date, there were 16,250,954 shares of First Connecticut common stock outstanding and entitled to vote at the special meeting, held by 1,613 holders of record. Each stockholder of record on that date is entitled to one vote for each share held on each proposal to be considered at the special meeting.

The presence (in person or by proxy) of holders of at least a majority of the shares entitled to vote at the special meeting constitutes a quorum for transacting business at the special meeting. All shares of First Connecticut common stock present in person or represented by proxy, including abstentions and broker non-votes, will be treated as present and entitled to vote for purposes of determining the presence or absence of a quorum for all matters voted on at the special meeting.

Vote Required, Treatment of Abstentions and Failure to Vote

Merger proposal:

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Compensation proposal:

Adjournment proposal:

First Connecticut’s stockholders must approve the merger proposal in order for the merger to occur. First Connecticut’s stockholders are not, however, required to approve the compensation proposal or the adjournment proposal in order for the merger to occur. If First Connecticut’s stockholders fail to approve the compensation proposal or the adjournment proposal, but approve the merger proposal, the merger may nonetheless occur.

Shares Held by First Connecticut Officers and Directors

As of the record date, the directors and executive officers of First Connecticut and their affiliates collectively owned, and were entitled to vote, 1,476,531 shares of First Connecticut common stock, representing approximately 9.1% of First Connecticut’s outstanding shares on that date. First Connecticut currently expects that each of its directors and executive officers and their affiliates will vote their shares of First Connecticut common stock “FOR” the approval of the merger proposal, although none of them has entered into an agreement requiring them to do so.

When considering the recommendation of First Connecticut’s board of directors that you vote in favor of the merger proposal, First Connecticut’s stockholders should be aware that certain of the directors and executive officers of First Connecticut have certain interests in the merger that may be different from, or in addition to, the interests of First Connecticut’s stockholders generally. First Connecticut’s board of directors was aware of these interests and considered them, among other matters, in making its recommendation that First Connecticut’s stockholders vote to approve the merger proposal. For more information, see “The Merger—Interests of First Connecticut’s Directors and Executive Officers in the Merger” beginning on page 59.

Voting of Proxies and Incomplete Proxies

A stockholder of First Connecticut may vote by proxy or in person at the special meeting. If you hold your shares of First Connecticut common stock in your name as a stockholder of record, you may authorize the persons named in the enclosed proxy card to vote your shares of First Connecticut common stock at the special meeting in the manner you direct by using one of the following methods:

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First Connecticut’s board of directors requests that you vote by completing, signing, dating and returning the enclosed proxy card to First Connecticut in the enclosed postage-paid envelope or by submitting a proxy through the Internet or by telephone as described on the enclosed instructions as soon as possible. If you intend to submit your proxy through the Internet or by telephone, you must do so by 11:59 P.M. Eastern Time on September 24, 2018, the day before the special meeting. If you intend to submit your proxy by mail, your completed proxy card must be received prior to the special meeting.

All properly signed proxies received prior to the special meeting and not revoked before the vote at the special meeting will be voted at the special meeting according to the instructions indicated on the proxies or, if no instructions are given, the shares of First Connecticut common stock will be voted “FOR” the merger proposal, “FOR” the compensation proposal and “FOR” the adjournment proposal; however, for those shares of First Connecticut common stock held in the Farmington Bank Employee Stock Ownership Plan (which we refer to as the “ESOP”) or in the Farmington Bank 401K Profit Sharing Plan (which we refer to as the “401K Plan”), if no instructions are given, such shares of First Connecticut common stock will be voted in the same proportion as votes received from other participants in the ESOP or the 401K Plan, as applicable.

Your vote is very important. Whether or not you plan to attend the special meeting, please take the time to vote by completing, signing, dating and returning the enclosed proxy card to First Connecticut in the enclosed postage-paid envelope or by submitting a proxy through the Internet or by telephone as described on the enclosed instructions as soon as possible to make sure your shares of First Connecticut common stock are represented at the special meeting. Submitting a proxy now will NOT prevent you from being able to attend and vote in person at the special meeting. Please vote, using one of the available methods described above, as soon as possible.

If you hold shares of First Connecticut common stock in “street name” through a bank, broker or other nominee, you should check the voting form provided to you by such bank, broker or other nominee to determine whether you may vote through the Internet or by telephone.

Shares Held in Street Name and Broker Non-Votes

If your shares of First Connecticut common stock are held in “street name” through a bank, broker or other nominee, meaning in the name of a bank, broker or other nominee who is the record holder, you must provide such record holder of your shares of First Connecticut common stock with instructions on how to vote your shares of First Connecticut common stock. Please follow the voting instructions provided by the bank, broker or other nominee. You may not vote your shares of First Connecticut common stock held in street name by returning a proxy card directly to First Connecticut or by voting in person at the special meeting, unless you provide a “legal proxy,” which you must obtain from your bank, broker or other nominee. Further, brokers, banks or other nominees who hold shares of First Connecticut common stock on behalf of their customers may not give a proxy to First Connecticut to vote those shares of First Connecticut common stock with respect to any of the proposals without specific instructions from their customers, as brokers, banks and other nominees do not have discretionary voting power on these matters. Therefore, failure to instruct your bank, broker or other nominee how to vote will have the same effect as a vote “AGAINST” approval of the proposals.

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