FIVE STAR SENIOR LIVING INC.Table of Contents

TABLE OF CONTENTS

2019 Proxy Statement    1

VOTING INFORMATIONTable of Contents

WE WANT TO HEAR FROM YOU – PLEASE VOTE TODAY

YourIt is very important that you vote is important.

ELIGIBILITY TO VOTE

You canto play a part in the future of our Company. The Nasdaq Stock Market LLC (the "Nasdaq") rules do not allow a broker, bank or other nominee who holds shares on your behalf to vote if you were a stockholder of record at the close of business on March 15, 2019.nondiscretionary matters without your instructions.

PROPOSALS THAT REQUIRE YOUR VOTE

PleaseYou can vote in advance in one of three ways:

via the internet		Visitwww.proxyvote.com and enter your 16-digit control number provided in your Notice Regarding the Availability of Proxy Materials, proxy card or voting instruction form before 11:59 p.m., Eastern time, on June 10, 20198, 2020 to authorize a proxyVIA THE INTERNET.
by phone		Call 1-800-690-6903 if you are a stockholder of record and 1-800-454-8683 if you are a beneficial owner before 11:59 p.m., Eastern time, on June 10, 20198, 2020 to authorize a proxyBY TELEPHONE.TELEPHONE. You will need the 16-digit control number provided on your Notice Regarding the Availability of Proxy Materials, proxy card or voting instruction form.
by mail		Sign, date and return your proxy card if you are a stockholder of record or voting instruction form if you are a beneficial owner to authorize a proxyBY MAIL.

If the meeting is postponed or adjourned, these times will be extended to 11:59 p.m., Eastern time, on the day before the reconvened meeting.

PLEASE VISIT:www.proxyvote.com

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To review and download easy to read versions of our Proxy Statement and Annual Report.



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To sign up for future electronic delivery to reduce the impact on the environment.

2    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement

SUMMARY OF PROPOSALS

This summary highlights matters for consideration by stockholders at our 2019 Annual Meeting. You should read this entire Proxy Statement carefully before voting. Page references are supplied to help you find further information in this Proxy Statement.

ELECTION OF BOARD NOMINEE (page 12)

Stockholders are voting to elect the following Director to our Company's Board of Directors.

The Board recommends that you vote "FOR" the election of Dr. Gans.

APPROVAL OF THE ISSUANCE OF COMMON SHARES OF THE COMPANY TO SNH AND SNH SHAREHOLDERS (page 15)

In light of our substantial operating and liquidity challenges, we and our independent auditors, RSM US LLP, have determined that there is substantial doubt about our ability to continue as a going concern. Despite the various strategic and operational changes we have made, we remained financially challenged with a deteriorating financial outlook and liquidity challenges. After evaluating multiple options, including seeking bankruptcy protection to reorganize our Company, we recently announced a transaction with SNH, our principal landlord and the owner of the senior living communities that we manage, to restructure our contractual arrangements in a manner we believe substantially improves our financial outlook. Issuing a substantial ownership stake to SNH and SNH shareholders is a condition to this restructuring.

Stockholders are voting to approve the issuance of up to 262,450,513 common shares of the Company to SNH and SNH shareholders in connection with the restructuring of our contractual arrangements with SNH to address our liquidity challenges and improve our long term financial outlook. This share issuance will result in (1) SNH owning up to approximately 34% of the outstanding common shares of the Company and (2) SNH shareholders owning approximately 51% of the outstanding common shares of the Company, after giving effect to the share issuance. In connection with the restructuring, SNH will pay to us $75.0 million as consideration for the share issuance.

The Board recommends that you vote "FOR" this proposal because approval of the share issuance is a condition to the restructuring of our contractual arrangements with SNH. As described in more detail below, we entered into this restructuring after a careful review of multiple options by a special committee of our Board comprised solely of our Independent Directors. The special committee engaged Citigroup Global Markets Inc. to act as financial advisor to the special committee in connection with its evaluation of the share issuance and the related transactions. Despite the resulting dilution to our existing stockholders, our Board believes approving the share issuance is in our Company's and our stockholders' best interests because our Board believes the restructuring of our contractual arrangements with SNH provides an immediate solution to our liquidity challenges, materially improves the long term financial outlook of our business and further invests SNH in our success.

FIVE STAR SENIOR LIVING INC.     20192020 Proxy Statement    3

RATIFICATION OF THE APPOINTMENT OF RSM US LLP AS INDEPENDENT AUDITORS (page 18)

Stockholders are voting to ratify the appointment of RSM US LLP as independent auditors of Five Star Senior Living Inc. for the Company's fiscal year ending December 31, 2019. The Company's Audit Committee evaluates the performance of the Company's independent auditors and determines whether to reengage the current independent auditors or consider other audit firms. In doing so, the Audit Committee considers the quality and efficiency of the services provided by the auditors, the auditors' technical expertise and knowledge of the Company's operations and industry, the auditors' independence, legal proceedings involving the auditors, the results of Public Company Accounting Oversight Board inspections and peer quality reviews of the auditors and the auditors' reputation in the marketplace. Based on its consideration of these matters, the Audit Committee has appointed RSM US LLP to serve as independent auditors for the fiscal year ending December 31, 2019.

The Board recommends you vote "FOR" the ratification of the appointment of RSM US LLP as independent auditors.

4    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement1

Table of Contents

FIVE STAR SENIOR LIVING INC.
400 CENTRE STREET
NEWTON, MASSACHUSETTS 02458April 15, 2020

April 25, 2019

PROXY STATEMENT

TheOur Board of Directors (the(our "Board") of Five Star Senior Living Inc., a Maryland corporation (the "Company," "we," "us" or "our") is furnishing this proxy statement (the "Proxy Statement") and accompanying proxy card (or voting instruction form) to you in connection with the solicitation of proxies by theour Board for the 2019our 2020 annual meeting of stockholders of the Company. Thestockholders. Our annual meeting will be held at Two Newton Place, 255 Washington Street, Suite 100, Newton, Massachusetts 02458^* on Tuesday, June 11, 2019,9, 2020, at 9:30 a.m., Eastern time, andsubject to any adjournmentspostponements or postponementsadjournments thereof (the "2019"2020 Annual Meeting"). We are first making these proxy materials available to stockholders on or about April 25, 2019.15, 2020.

Only owners of record of shares of common stock of the Company ("Common Shares") as of the close of business on March 15, 2019,16, 2020, the record date for the meeting,2020 Annual Meeting, are entitled to notice of, and to vote at, the meeting and at any postponements or adjournments of the meeting. Holders of Common Shares are entitled to one vote for each Common Share held on the record date. On March 15, 2019,16, 2020, there were approximately 50,846,55231,543,711 Common Shares issued and outstanding.

The mailing address of the Company'sour principal executive officesoffice is 400 Centre Street, Newton, Massachusetts 02458.

* As part of our precautions regarding the coronavirus or COVID-19, we are planning for the possibility that the annual meeting may be held virtually solely by means of remote communication or via a live webcast. If we take this step, we will announce the decision to do so in advance, and we will provide details on how to participate in a press release and on our website atwww.fivestarseniorliving.com.

FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement    5

QUESTIONS AND ANSWERS

Proxy Materials and Voting Information

The proxy materials for the 2019 Annual Meeting include the Notice Regarding the Availability of Proxy Materials, Notice of 2019 Annual Meeting, this Proxy Statement and the Company's Annual Report to Stockholders for the fiscal year ended December 31, 2018 (the "Annual Report" and, together with the other materials, the "proxy materials"). If you request a paper copy of these materials, the proxy materials will also include a proxy card or voting instruction form.

A proxy statement is a document that the Securities and Exchange Commission ("SEC") regulations require the Company to give you when it asks you to return a proxy designating individuals to vote on your behalf. A proxy is your legal designation of another person to vote the shares you own. That other person is called your proxy. We are asking you to designate the following three persons as your proxies for the 2019 Annual Meeting: Jennifer B. Clark, Secretary; Adam D. Portnoy, Managing Director; and Katherine E. Potter, President and Chief Executive Officer.

If your shares are registered directly in your name with the Company's registrar and transfer agent, Equiniti Shareowner Services, you are considered a stockholder of record of those shares. If you are a stockholder of record, you should receive only one notice or proxy card for all the Common Shares you hold in certificate form and in book entry form.

If your shares are held in an account you own at a bank or brokerage or you hold shares through another nominee, you are considered the "beneficial owner" of those shares. If you are a beneficial owner, you will receive voting instruction information from the bank, broker or other nominee through which you own your Common Shares.

If you hold some shares of record and some shares beneficially, you should receive a notice or proxy card for all the Common Shares you hold of record and a separate voting instruction form for the shares from the bank, broker or other nominee through which you own Common Shares.

By Written Proxy. All stockholders of record can submit voting instructions by written proxy card. If you are a stockholder of record and receive a Notice Regarding the Availability of Proxy Materials, you may request a written proxy card by following the instructions included in the notice. If you are a beneficial owner, you may request a written proxy card or a voting instruction form from your bank, broker or other nominee. Proxies submitted by mail must be received by 11:59 p.m., Eastern time, on June 10, 2019 or, if the meeting is postponed or adjourned to a later date, by 11:59 p.m., Eastern time, on the day immediately preceding the date of the reconvened meeting.

By Telephone or Internet. All stockholders of record also can authorize a proxy to vote their shares by touchtone telephone by calling 1-800-690-6903, or through the internet atwww.proxyvote.com, using the procedures and instructions described in your Notice Regarding the Availability of Proxy Materials or proxy card. Beneficial owners may authorize a proxy by telephone or internet if their bank, broker or other

6    2    FIVE STAR SENIOR LIVING INC.     20192020 Proxy Statement

nominee makes those methods available, in which case the bank, broker or nominee will include the instructions with the proxy voting materials. To authorize a proxy by telephone or internet, you will need the 16-digit control number provided on your Notice Regarding the Availability of Proxy Materials, proxy card or voting instruction form. The telephone and internet proxy authorization procedures are designed to authenticate stockholder identities, to allow stockholders to vote their shares and to confirm that their instructions have been recorded properly. Proxies submitted by telephone or through the internet must be received by 11:59 p.m., Eastern time, on June 10, 2019 or, if the meeting is postponed or adjourned to a later date, by 11:59 p.m., Eastern time, on the day immediately preceding the date of the reconvened meeting.

In Person.Table of Contents

All stockholders of record may vote in person at the meeting. Beneficial owners may vote in person at the meeting if they have a legal proxy, as described in the response toquestion 16. If you have any questions or need assistance in voting your shares or authorizing your proxy, please call the firm assisting the Company in the solicitation of proxies:CORPORATE GOVERNANCE PRINCIPLES AND BOARD MATTERS

Morrow Sodali LLC
470 West Avenue
Stamford, Connecticut 06902
Stockholders Call Toll Free: (800) 662-5200
Banks and Brokers Call Collect: (203) 658-9400

HoldersWe are currently governed by a seven member Board of recordDirectors. Ensuring our Board is comprised of Common Shares asDirectors who bring diverse viewpoints and perspectives, exhibit a variety of skills, professional experience and backgrounds and effectively represent the closelong term interests of business on March 15, 2019, the record date, may vote at the meeting. Holdersstockholders is a top priority of Common Shares are entitled to one vote for each Common Share held on the record date.our Board and our Nominating and Governance Committee.

OUR BOARD BELIEVES THAT ITS MEMBERS SHOULD:

If you submitIn addition, our Board has determined that our Board, as a signed proxy card or authorize a proxy by internet or telephone, but do not indicate how your Common Shareswhole, should be voted onstrive to have the right mix of characteristics and skills necessary to effectively perform its oversight responsibilities. Our Board believes that Directors with one or more proposals, thenof the proxies will vote your shares as the Board recommends on those proposals. Other than the proposals listed on pages 12, 15 and 18, we do not know of any other matters to be presented at the meeting. If any other matters are properly presented at thefollowing professional skills or experiences can assist in meeting the proxies may vote your shares in accordance with their best judgment.this goal:

A quorumOur Nominating and Governance Committee and our Board consider the qualifications, characteristics and skills of stockholders is requiredDirectors and Director candidates individually and in the broader context of our Board's overall composition when evaluating potential nominees for stockholders to take action at the 2019 Annual Meeting. The presence, in person or by proxy, of stockholders entitled to cast one-third of all the votes entitled to be cast at the 2019 Annual Meeting constitutes a quorum.

Abstentions and broker non-votes are included in determining whether a quorum is present. Abstentions are not votes cast and, therefore, will not be included in vote totals and will have no effect on the outcome of any Item to be voted on at the 2019 Annual Meeting. A proxy marked "WITHHOLD" with respect to Item 1 will have the same effectelection as an abstention. Broker non-votes are not votes cast and, therefore, will not be included in vote totals and will have no effect on the outcome of Item 1 or Item 2. There can be no broker non-votes on Item 3 as it is a matter on which, if you hold your shares in street name and do not provide voting instructions to the broker, bank or other nominee that holds your shares, the nominee has discretionary authority to vote on your behalf.Director.

FIVE STAR SENIOR LIVING INC.     20192020 Proxy Statement    73

Table of Contents

Stockholders have the right to revoke a proxy at any time before it is voted at the 2019 Annual Meeting, subject to the proxy voting deadlines described above. Stockholders may revoke a proxy by authorizing a proxy again on a later date by internet or by telephone (only the last internet or telephone proxy submitted prior to the meeting will be counted) or by signing and returning a later dated proxy card or by attending the meeting and voting in person. If you are a beneficial owner, see the response toquestion 16.

A stockholder's attendance at the 2019 Annual Meeting will not revoke that stockholder's proxy unless that stockholder votes again at the meeting or sends an original written statement to the Secretary of the Company revoking the prior proxy. An original written notice of revocation or subsequent proxy should be delivered to Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458, Attention: Secretary, or hand delivered to the Secretary before the taking of the vote at the 2019 Annual Meeting.

Beneficial owners who wish to change their votes should contact the organization that holds their shares.

The NoticeOur Board is elected by stockholders to oversee our business and long term strategy. As part of 2019 Annual Meeting, this Proxy Statementfulfilling its responsibilities, our Board oversees the safeguarding of our assets, the maintenance of appropriate financial and other internal controls and our compliance with applicable laws and regulations. Inherent in these responsibilities is our Board's understanding and oversight of the Annual Report are available atvarious risks we face. Our Board considers that risks should not be viewed in isolation and should be considered in virtually every business decision and as part of our business strategy.

Our Board oversees risk as part of its general oversight of our Company. Oversight of risk is addressed as part of various Board and Board committee activities and through regular and special Board and Board committee meetings. Our day to day business is conducted by management, and management is responsible for incorporating risk management in its activities. Our Director of Internal Audit reports to our Audit Committee and provides us advice and assistance with our risk management function.

In discharging their oversight responsibilities, our Board and Board committees review regularly a wide range of reports provided to them by management, internal audit and service providers, including:

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reports on market and industry conditions;www.proxyvote.com



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operating and regulatory compliance reports;. You



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reports on clinical operations;



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financial reports;



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reports on risk management activities;



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regulatory and legislative updates that may access these proxy materialsimpact us;



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reports on the internet through the conclusionsecurity of the 2019 Annual Meeting.

Instead of receiving future copies of the Company's proxy materials by mail, stockholders of recordour information technology processes and most beneficial owners may elect to receive these materials electronically. Opting to receive your future proxy materials electronically will save us the cost of printingour data; and mailing documents,



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legal proceedings updates and also will give you an electronic link to our proxy voting site. Your Notice Regarding the Availability of Proxy Materials instructs you as to how you may request electronic delivery of future proxy materials.

9.    How are proxies solicited and what is the cost?

The Company bears all expenses incurred in connection with the solicitation of proxies. The Company has engaged Morrow Sodali LLC ("Morrow") to assist with the solicitation of proxies for an estimated fee of $10,000 plus reimbursement of expenses. The Company has agreed to indemnify Morrow against certain liabilities arising out of the Company's agreement with Morrow. We will request banks, brokers andreports on other nominees to forward proxy materials to the beneficial owners of Common Shares and to obtain their voting instructions. We will reimburse those firms for their expenses of forwarding proxy materials.

Proxies may also be solicited, without additional compensation, by the Company's and its subsidiaries' directors, officers and employees, and by The RMR Group LLC ("RMR LLC"), its officers and employees and its parent's and subsidiaries' directors, officers and employees, by mail, telephone or other electronic means or in person.

10.    What is householding?

As permitted by the Securities Exchange Act of 1934, as amended (the "Exchange Act"), we may deliver only one copy of the Notice Regarding the Availability of Proxy Materials, Notice of 2019 Annual Meeting, this Proxy Statement and the Annual Report to stockholders residing at the same address, unless the stockholders have notified us of their desire to receive multiple copies of those documents. This practice is known as "householding."

business related matters.

8    4    FIVE STAR SENIOR LIVING INC.     20192020 Proxy Statement

We will deliverTable of Contents

Our Board and Board committees discuss these matters among themselves and with our management, our Director of Internal Audit, legal counsel, our independent auditors and other professionals, as appropriate.

Our Audit Committee takes a separate copy of any of those documents to you if you write to the Company at Investor Relations, Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458, or call the Company at (617) 796-8245. If you want to receive separate copiesleading role in helping our Board fulfill its responsibilities for oversight of our noticesfinancial reporting, internal audit function, risk management and our compliance with legal and regulatory requirements. Our Board and Audit Committee review periodic reports from our independent auditors regarding potential risks, including risks related to our internal control over financial reporting. Our Audit Committee also reviews, approves and oversees an internal audit plan developed by our Director of Internal Audit with the availabilitygoal of proxy materials, noticeshelping us systematically evaluate the effectiveness of its risk management, control and governance processes on an annual meetings, proxy statementsbasis. Our Audit Committee considers risks related to cybersecurity and annualreceives regular reports from management regarding cybersecurity risks and countermeasures being undertaken or considered by us, including updates on the internal and external cybersecurity landscape and relevant technical developments. Our Audit Committee meets at least quarterly and reports its findings to our Board. Our Audit Committee also meets periodically with our Director of Internal Audit to review the results of our internal audits, and directs or recommends to our Board actions or changes it determines appropriate to enhance or improve the effectiveness of our risk management.

Our Quality of Care Committee reviews management reports on our clinical operations and directs or recommends to management and our Board actions or changes it determines appropriate to improve our clinical operations and to reduce risks arising from those operations.

Our Compensation Committee whose duties are detailed in its charter, among other duties, evaluates the performance of our Director of Internal Audit and the performance of The RMR Group LLC ("RMR LLC") under our business management agreements. Also, our Compensation Committee and our Board consider that we have a share award program that requires share awards to executive officers to vest over a period of years. We believe that the use of share awards vesting over time rather than stock options mitigates the incentives for our management to undertake undue risks and encourages management to make longer term and appropriately risk balanced decisions.

It is not possible to identify all of the risks that may affect us or to develop processes and controls to eliminate all risks and their possible effects, and processes and controls employed to address risks may be limited in their effectiveness. Moreover, it is necessary for us to bear certain risks to achieve our objectives. As a result of the foregoing and other factors, our ability to manage risk is subject to substantial limitations.

To learn more about the risks we face, you can review the matters discussed in Part I, "Item 1A. Risk Factors" and "Warning Concerning Forward Looking Statements" in our Annual Report for the year ended December 31, 2019 (the "Annual Report"). The risks described in the Annual Report are not the only risks we face. Additional risks and uncertainties not currently known or that may currently be deemed to be immaterial also may materially adversely affect our business, financial condition or results of operations in future or if you are receiving multiple copies and would like to receive only one copy per household, you should contact your bank, broker or other nominee, or you may contact us at the above address or telephone number.periods.

Share Issuance Proposal

The issuanceUnder the corporate governance listing standards of upthe Nasdaq, to 262,450,513 Common Shares to Senior Housing Properties Trust ("SNH")be considered independent:

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a director must not have a disqualifying relationship, as defined in the corporate governance section of the Nasdaq rules; and SNH shareholders (the "Share Issuance") is a condition to the restructuring of



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our contractual arrangements with SNH. This restructuring was agreed to address our operating and liquidity challenges and our deteriorating financial outlook. The Nasdaq Stock Market LLC's (the "Nasdaq") Listing Rules requireBoard must affirmatively determine that the Share Issuance be approved bydirector otherwise has no relationship which would interfere with the exercise of independent judgment in carrying out the responsibilities of a majority ofdirector. To facilitate the votes cast by our stockholders.

12.    Why does the Board recommend that the Company's stockholders approve the Share Issuance proposal?

In light of our substantial operating and liquidity challenges, we and our independent auditors, RSM US LLP, have determined that there is substantial doubt about our ability to continue as a going concern. After evaluating multiple options, including seeking bankruptcy protection to reorganize our Company, we entered into a transaction with SNH, our principal landlord and the owner of the senior living communities that we manage, to restructure our contractual arrangements. Although the Share Issuance would result in substantial dilution to our existing stockholders,director independence assessment process, our Board believes ithas adopted written Governance Guidelines as described below.

Our Board is in your and our Company's best interests because our Board believes the restructuringcomprised of our contractual arrangements with SNH provides an immediate solution to our liquidity challenges, materially improves the long term financial outlook of our business and further invests SNH in our success. Absent this restructuring, our Board does not believe that we will be able to continue as a going concern. However, with this restructuring, our Board believes that we will be able to weather the current industry challenges and position ourselves for future success.

Yes. The decision to enter the Restructuring Transaction (as defined below under the section entitled "Certain Related Person Transactions") was the result of numerous meetings of a special committee of our Board comprised solely of ourseven Directors, including five Independent Directors and its advisors overtwo Managing Directors. Under our Bylaws, so long as the past several months. The special committee evaluated multiple options, and engaged in extensive negotiations with the special committeenumber of the board of trustees of SNH, to find a solution that would address our deteriorating financial outlook and liquidity challenges, ranging from the restructuring of our contractual arrangements with SNH to seeking bankruptcy protection to reorganize our Company. Although the Share Issuance would result in substantial dilution to our existing stockholders, our Board believes the Restructuring Transaction, including the Share Issuance,directors is in the best interests of our Company and our existing stockholders because it provides an immediate solution to our liquidity challenges, materially improves the long term financial outlook for our business and further invests SNH in our success.less than five, at least one director

FIVE STAR SENIOR LIVING INC.     20192020 Proxy Statement    9

If stockholders do not approve the Share Issuance by December 31, 2019, we will not issue any Common Shares to SNH or its shareholders, and SNH may terminate our restructuring agreement. If such termination occurs, our restructuring agreement provides that our contractual agreements revert to the terms in effect immediately prior to the execution of our restructuring agreement. This means that our existing historical contractual arrangements with SNH will be restored and, among other things, we will again be obligated to pay minimum rent under our leases with SNH at the contractual lease rate which, as of the date hereof, is $17.4 million of base rent (which is $6.4 million more per month than the restructured amount). We will also need to repay any amounts owed to SNH under the credit facility it has extended to us and we will not receive the consideration SNH would otherwise have paid for the Share Issuance. As a result, we will likely default on our rent obligations owed to SNH and under our credit facilities. If we default on our leases with SNH or either of our credit facilities and do not obtain relief for that default we will be forced to consider other options, including filing for bankruptcy protection and/or ceasing our operations.

2019 Annual Meeting Information

Attendance at the meeting is limited to the Company's Directors and officers, stockholders as of the record date (March 15, 2019) or their duly authorized representatives or proxies, and other persons permitted by the Chairman of the meeting. All attendees need to bring photo identification for admission.

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Record owners: If you are a stockholder as of the record date who holds shares directly, you need not present any documentation to attend the 2019 Annual Meeting, other than photo identification.



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Beneficial owners: If you are a stockholder as of the record date who holds shares indirectly through a brokerage firm, bank or other nominee, you must present evidence of your beneficial ownership of shares. For this purpose, a copy of a letter or account statement from the applicable brokerage firm, bank or other nominee confirming such ownership will be acceptable and such copy may be retained by the Company. Please note that you will not be able to vote your shares at the meeting without a legal proxy, as described in the response toquestion 16.

If you have questions regarding these admission procedures, please call Investor Relations at (617) 796-8245.

If you are a beneficial owner and want to vote your shares at the 2019 Annual Meeting, you need a legal proxy from your bank, broker or other nominee. You also need to follow the procedures described in the response toquestion 15 and to bring the legal proxy with you to the meeting and hand it in with a signed ballot that will be provided to you at the meeting. You will not be able to vote your shares at the meeting without a legal proxy. If you do not have a legal proxy, you can still attend the meeting by following the procedures described in the response toquestion 15. However, you will not be able to vote your shares at the meeting without a legal proxy. The Company encourages you to vote your shares in advance, even if you intend to attend the meeting.

10    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement5

Company Documents, Communications and Stockholder Proposals

You can visit our website to view our Governance Guidelines, Board committee charters and CodeTable of Business Conduct and Ethics (the "Code"). To view these documents, go towww.fivestarseniorliving.com, click on "Investor Relations" and then click on "Corporate Governance." To view the Company's SEC filings and Forms 3, 4 and 5 filed by the Company's Directors and executive officers, go towww.fivestarseniorliving.com, click on "Investor Relations" and then click on "Financial Information & SEC Filings."

We will deliver free of charge, upon request, a copy of the Company's Governance Guidelines, Board committee charters, the Code or the Annual Report to any stockholder requesting a copy. Requests should be directed to Investor Relations at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458.

Any stockholder or other interested person who wants to communicate with the Company's Directors, individually or as a group, should write to the party for whom the communication is intended, c/o Secretary, Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458 or email secretary@5ssl.com. The communication will then be delivered to the appropriate party or parties.

A proposal for action to be presented by any stockholder at the Company's 2020 annual meeting of stockholders must be submitted as follows:

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For a proposal to be eligible to be included in the proxy statement pursuant to Rule 14a-8 under the Exchange Act, the proposal must be received at the Company's principal executive offices by December 27, 2019.

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If the proposal is not to be included in the proxy statement pursuant to Rule 14a-8, the proposal must be made in accordance with the procedures and requirements set forth in our Bylaws and must be received by the Company not later than 5:00 p.m., Eastern time, on December 27, 2019 and not earlier than November 27, 2019.

Proposals should be sent to the Company's Secretary at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458.

For additional information regarding how to submit a stockholder proposal, see page 37 of this Proxy Statement.

Contents

ELECTION OF DIRECTOR (ITEM 1)

Stockholders are voting to electmust meet the Board nominee, Bruce M. Gans, M.D., to our Board.

The Board servesqualifications of a Managing Director and, so long as the decision making bodynumber of directors is five or greater, at least two directors must meet the Company, except for those matters reserved to the stockholders. Thequalifications of a Managing Director. Our Bylaws require that a majority of our Board selects and oversees the Company's officers, who are charged by the Board with conducting the day to day business of the Company.

In accordance with our Charter, the Board currently consists of five Directors, three of whom are Independent Directors and two of whom are Managing Directors. Our Charter provides that the Board is divided into three groups, with Directors of each group serving for a term that expires at the third annual meeting of stockholders following his or her election and until his or her successor is duly elected and qualifies.

Assuming a quorum is present at the meeting, a plurality of all the votes cast at the meeting is required to elect a Director at the 2019 Annual Meeting.

Directors are responsible for overseeing the Company's business. This significant responsibility requires highly skilled individuals with various qualities, attributes and professional experience. The Board believes that there are general requirements that are applicable to all Directors, qualifications applicable to Independent Directors and other skills and experience that should be represented on the Board as a whole, but not necessarily by each Director. In accordance with our Charter and Bylaws, the Board consists of five Directors: two Managing Directors and three Independent Directors. As set forth inUnder our Bylaws, Independent Directors are Directors who are not employees of the Company or RMR LLC, who are not involved in the Company's day to day activities and are persons who meet the qualifications ofqualify as independent directors under the applicable rules and requirements of the Nasdaq and the SEC. As set forth in our Bylaws, Managing Directors are Directors who are not Independent Directors and who have been employees of the Company or RMR LLC or any of its subsidiaries or involved in the day to day activities of the Company, any of its subsidiaries or any of their predecessors for at least one year prior to such Director's election.

Our Board affirmatively determines whether Directors have a direct or indirect material relationship with the Company, including the Company's subsidiaries, other than serving as our Directors or trustees or directors of our subsidiaries. In making independence determinations, our Board observes the Nasdaq and SEC criteria, as well as the criteria set forth in our governing documents. When assessing a Director's relationship with us, our Board considers all relevant facts and circumstances, not merely from the Director's standpoint, but also from that of the persons or organizations with which the Director has an affiliation. Based on this review, our Board has determined that Barbara D. Gilmore, Donna D. Fraiche, Bruce M. Gans, M.D., Gerard M. Martin and Michael E. Wagner, M.D. currently qualify as independent directors under applicable Nasdaq and SEC criteria and as Independent Directors under our Bylaws. In making these independence determinations, our Board reviewed and discussed additional information provided by us and our Directors with regard to each of the Directors' relationships with us, RMR LLC or The RMR Group Inc. ("RMR Inc."), the managing member of RMR LLC, and the other companies to which RMR LLC or its subsidiaries provide management services. Our Board has concluded that none of these five Directors possessed or currently possesses any relationship that could impair his or her judgment in connection with his or her duties and responsibilities as a Director or that could otherwise be a direct or indirect material relationship under applicable Nasdaq and SEC standards.

Pursuant to our Governance Guidelines, our Independent Directors are expected to meet in regularly scheduled meetings at which only Independent Directors are present. It is expected that these executive sessions may occur at least twice per year. Our Independent Directors also meet separately with our officers, with our Director of Internal Audit and with our independent auditors. The presiding Director for purposes of leading Independent Director sessions will be the Lead Independent Director, unless the Independent Directors determine otherwise.

All Directors play an active role in overseeing our business both at the Board and committee levels. As set forth in our Governance Guidelines, the core responsibility of our Directors is to exercise sound, informed and independent business judgment in overseeing the Company and its strategic direction. Our Directors are skilled and experienced leaders and currently serve or have served as members of senior management in public and private for profit and nonprofit organizations, and also have served in academia. Our Directors may be called upon to provide solutions to various complex issues and are expected to, and do, ask hard questions of our officers and advisers. Our Board is small, which facilitates informal discussions and communication from management to our Board and among Directors.

Adam D. Portnoy has served as Chair of our Board since 2019. One or more of our executive officers and our Director of Internal Audit are not members of our Board and regularly attend Board and Board committee meetings. Special meetings of our Board may be called at any time by the President, any Managing Director or any two Directors. Our Managing Directors, in consultation with our management and our Director of Internal Audit, set the agenda for Board meetings. Other Directors may suggest agenda items as well. Discussions at Board meetings are led by the Managing Director or Independent Director who is most knowledgeable on a subject.

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Five of our Directors, including one of our nominees for election at the 2020 Annual Meeting, are independent under the applicable Nasdaq and SEC criteria and our governing documents. All of the members of our Audit Committee, Nominating and Governance Committee and Compensation Committee are independent under the applicable listing requirements and rules of the Nasdaq and other applicable laws, rules and regulations, including those of the SEC. As set forth in our governing documents, two of our Directors are Managing Directors, persons who have been employees, officers or directors of the Company or RMR LLC or who have been involved in the Company's day to day activities for at least one year prior to their electionsuch Director's election.

We have a Lead Independent Director who is selected annually by the vote of a majority of our Independent Directors. Currently, Ms. Fraiche serves as Directors. Theour Lead Independent Director. Our Lead Independent Director has well-defined, substantive responsibilities that include:

•

presiding at all meetings of our Board at which the Chair or a Managing Director is not present;



•

presiding at all meetings and executive sessions of the Independent Directors;



•

having the authority to call meetings of the Independent Directors or executive sessions of the Independent Directors;



•

serving as the principal liaison between the Independent Directors and the senior management team;



•

arranging, together with the Chair of our Board, for appropriate information (including quality and quantity) to be timely provided to our Board and the Independent Directors;



•

assisting our Compensation Committee in its annual evaluation of the performance of our management and of our manager, RMR LLC;



•

assisting with setting Board meeting agendas and arranging meeting schedules, including to ensure that there is sufficient time for discussion of all agenda items;



•

considering suggestions for meeting agenda items from other Independent Directors;



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authorizing the retention of advisors and consultants who report directly to the Independent Directors when appropriate; and



•

if requested, and in coordination with the Chair of our Board and the Company's management, being reasonably available for consultation and direct communication with stockholders.

Our Board is committed to corporate governance that promotes the long term interests of our stockholders. Our Board has established Governance Guidelines that provide a framework for effective governance. Our Board regularly reviews developments in corporate governance and updates our Governance Guidelines and other governance materials as it deems necessary and appropriate.

We have also adopted a Code of Business Conduct and Ethics (the "Code") to, among other things, provide guidance to our and our subsidiaries' directors, officers and employees and RMR LLC, its officers and employees and its parent's and subsidiaries' directors, officers and employees to ensure compliance with applicable laws and regulations.

Our Board has an Audit Committee, Compensation Committee, Nominating and Governance Committee consider the qualificationsand Quality of Directors and Director candidates individually and in the broader context of the Board's overall composition and the Company's current and future needs.

Qualifications for All Directors

In its assessment of each potential candidate, theCare Committee. Our Audit Committee, Compensation Committee, Nominating and Governance Committee considers the potential nominee's integrity, experience, achievements, judgment, intelligence, competence, personal character, likelihood thatand Quality of Care Committee each have adopted a candidate will be ablewritten charter, and reviews its written charter on an annual basis to serve on the Board for an extended period and other matters that theconsider whether any changes are required.

Our Audit Committee, Compensation Committee, Nominating and Governance Committee deems appropriate. The Nominating and GovernanceQuality of Care Committee are comprised entirely of Independent Directors under applicable Nasdaq rules who also takes into accountmeet the ability of a potential nomineeindependence criteria applicable to devoteaudit committees under the time and effort necessary to fulfill his or her responsibilities to the Company.

The Board and Nominating and Governance Committee require that each Director candidate be a person of high integrity with a proven record of success in his or her field. Each Director candidate must demonstrate the ability to make independent analytical inquiries, familiarity with and respect for corporate governance requirements and practices and a commitment to serving the Company's long term best interests. In addition, the Nominating and Governance Committee may conduct interviews of potential Director candidates to assess intangible qualities, including the individual's ability to ask appropriate questions and to work collegially. The Board does not have a specific diversity policy in connection with the selection of nominees for Director, but due consideration is given to the Board's overall balance of diversity of perspectives, backgrounds and experiences.

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Specific Qualifications, Attributes, Skills and Experience to be Represented on the Board

The Board has identified particular qualifications, attributes, skills and experience that are important to be represented on the Board as a whole, in light of the Company's long term interests. The following table summarizes certain key characteristics of the Company's businessSarbanes Oxley Act and the associated qualifications, attributes, skills and experienceSEC's implementing rules under that the Board believes should be represented on the Board.law.

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Our corporate governance materials are available for review in the governance section of our website, including our Governance Guidelines, the charter for each Board committee, the Code and information on how to report concerns or complaints about accounting, internal accounting controls or auditing matters and any violations or possible violations of the Code and how to communicate with our Directors, individually or as a group. To access these documents on our website, visitwww.fivestarseniorliving.com.

Our Insider Trading Policies and Procedures expressly prohibits members of our Board and our officers from engaging in hedging transactions involving our securities and those of RMR Inc. or any other public company to which RMR LLC or its affiliates provide management services.

Our Nominating and Governance Committee is responsible for identifying and evaluating nominees for Director and for recommending to our Board nominees for election at each annual meeting of stockholders. Our Nominating and Governance Committee may consider candidates suggested by our Directors, officers or stockholders or by others. Stockholders who would like to recommend a nominee for the position of Director should submit their recommendations in writing by mail to the Chair of our Nominating and Governance Committee, c/o Five Star Senior Living Inc., Secretary, at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458 or by email to secretary@fivestarseniorliving.com. Any such recommendation should include a description of the candidate's qualifications for Board service, the candidate's written consent to be considered for nomination and to serve if nominated and elected, as well as the addresses and telephone numbers for contacting the stockholder and the candidate for more information. Our Nominating and Governance Committee may request additional information about the stockholder recommended nominee or about the stockholder recommending the nominee. Recommendations by stockholders will be considered by our Nominating and Governance Committee in its discretion using the same criteria as other candidates it considers.

Our Board has established a process to facilitate communication by stockholders and other interested parties with Directors. Communications should be addressed to Directors in care of the Secretary, Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458 or by email to secretary@fivestarseniorliving.com.

We understand the importance of leading a sustainable business and regularly consider ways to improve our internal culture and the communities in which we operate. Our environmental sustainability and community engagement strategies focus on a complementary set of objectives, including the following:

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Embrace Our Communities:We recognize the importance of aligning ourselves with the communities where we operate our senior living communities. We seek to be a responsible corporate citizen and to strengthen the communities in which we own or operate our senior living communities. We regularly encourage our employees to engage in a variety of charitable and community programs.



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Environmental Stewardship:Preserving our natural resources has a special meaning to us and to RMR LLC and its stakeholders. We support environmental practices that reduce the impact we have on our planet. We believe this is important to all our stakeholders, including investors, regulatory agencies, local communities, residents and employees. We seek to improve the environmental footprint of our properties, including by reducing energy consumption and water

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usage at our properties, especially when doing so may reduce operating costs and improve the properties' competitive positions. Through our Green Stars Program—we strive to achieve results by using resources more efficiently, minimizing waste, and increasing awareness among employees and residents.

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Diversity:We value a diversity of backgrounds, experience and perspectives. Our Chief Executive Officer is a woman and our Board is comprised of more than 40% women. We are an equal opportunity employer.

To learn more about our sustainability initiatives, visitwww.fivestarseniorliving.com/the-five-star-difference/green-stars-program.

The following table sets forthDeadline to Submit Proposals pursuant to Rule 14a-8 for the names2021 Annual Meeting of Stockholders: Stockholder proposals pursuant to Rule 14a-8 under the Securities Exchange Act of 1934, as amended (the "Exchange Act") must be received at our principal executive offices on or before December 16, 2020 in order to be eligible to be included in the proxy statement for the 2021 annual meeting of stockholders; provided, that, if the date of the Director nominee2021 annual meeting of stockholders is more than 30 days before or after June 9, 2021, such a proposal must be submitted within a reasonable time before we begin to print our proxy materials. Under Rule 14a-8, we are not required to include stockholder proposals in our proxy materials in certain circumstances or if conditions specified in the rule are not met.

Deadline to Submit Nominations and Other Proposals for the 2021 Annual Meeting of Stockholders Under our Bylaws: To be timely, stockholder nominations and proposals intended to be made outside of Rule 14a-8 under the Exchange Act at the 2021 annual meeting must be received by our Secretary at our principal executive offices, in accordance with the requirements of our Bylaws, not later than 5:00 p.m., Eastern time, on December 16, 2020 and not earlier than November 16, 2020; provided, that, if the date of the 2021 annual meeting of stockholders is more than 30 days earlier or later than June 9, 2021, then a stockholder's notice must be so delivered not later than 5:00 p.m., Eastern time, on the tenth day following the earlier of the day on which (i) notice of the date of the 2021 annual meeting of stockholders is mailed or otherwise made available or (ii) public announcement of the date of the 2021 annual meeting of stockholders is first made by us. Stockholders making such a nomination or proposal must comply with the advance notice and other requirements set forth in our Charter and Bylaws, which include, among other things, requirements as to the stockholder's timely delivery of advance notice, continuous requisite ownership of Common Shares, holding of a share certificate for such shares at the time of the advance notice and submission of specified information.

The foregoing description of the deadlines and other requirements for stockholders to submit a nomination for election to our Board or proposal of other business for consideration at an annual meeting of stockholders is only a summary and is not a complete listing of all requirements. Copies of our Bylaws, including the requirements for stockholder nominations and other stockholder proposals, may be obtained by writing to our Secretary at Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458, or from the SEC's website,www.sec.gov. Any stockholder considering making a nomination or proposal should carefully review and comply with those Directors who will continue to serve after the 2019 Annual Meeting:provisions.

Upon the recommendation of theour Nominating and Governance Committee, theour Board has nominated Dr. GansAdam D. Portnoy for election as a Managing Director and Barbara D. Gilmore for election as an Independent Director. Each Director in Group III. Dr. Gansnominee currently serves on theour Board. If elected, Dr. Ganseach of Mr. Portnoy and Ms. Gilmore would serve until the Company's 20222023 annual meeting of stockholders and until his or her successor is duly elected and qualifies.qualifies, subject to the individual's earlier death, resignation, retirement, disqualification or removal.

We expect thethat each nominee for election as a Director will be able to serve if elected. However, if thea nominee should become unable or unwilling to serve, proxies may be voted for the election of a substitute nominee designated by theour Board.

A plurality of all the votes cast is required to elect a Director at the 2020 Annual Meeting.

The Board believes that the combination of the various qualifications, attributes, skillsnames, principal occupations and experiences of the Director nominee would contribute to an effective Board serving the Company's long term best interests. The Boardcertain other information and the Nominating and Governance Committee believe that the Director nominee possesses the necessary qualifications to provide effective oversightnominees for Directors, as well as a summary of the business and quality advice and counsel to the Company's management. For further information regarding the key experiences, qualifications, attributes and skills that led theour Nominating and Governance Committee and theour Board to conclude that such person ispersons are currently qualified to serve as a Director, please seeDirectors, are set forth on the section entitled "Directors and Executive Officers".following pages.

TheOur Board of Directors recommends a vote "FOR" the election of theboth Director nominee.nominees.

14    10    FIVE STAR SENIOR LIVING INC.     2019 Proxy Statement

APPROVAL OF THE COMMON SHARE ISSUANCE TO SNH AND SNH SHAREHOLDERS (ITEM 2)

Stockholders are voting to approve the issuance of up to 262,450,513 Common Shares to SNH and SNH shareholders in connection with the restructuring of our contractual arrangements with SNH to address our liquidity challenges and improve our long term financial outlook. The Share Issuance will result in (1) SNH owning up to approximately 34% of the outstanding Common Shares and (2) SNH shareholders owning approximately 51% of the outstanding Common Shares, after giving effect to the Share Issuance. In connection with the restructuring, SNH will pay to us $75.0 million as consideration for the Share Issuance.

In light of our substantial operating and liquidity challenges, we and our independent auditors, RSM US LLP, have determined that there is substantial doubt about our ability to continue as a going concern. Despite the various strategic and operational changes we have made, we remained financially challenged with a deteriorating financial outlook and liquidity challenges. After evaluating multiple options, including seeking bankruptcy protection to reorganize our Company, we recently announced a transaction with SNH, our principal landlord and the owner of the senior living communities that we manage, to restructure our contractual arrangements. Issuing a substantial ownership stake to SNH and SNH shareholders is a condition to this restructuring.

The Board recommends that you vote "FOR" the proposal because approval of the Share Issuance is a condition to the restructuring of our contractual arrangements with SNH. As described in more detail below, we entered into this restructuring after a careful review of multiple options by a special committee of our Board comprised solely of our Independent Directors. The special committee engaged Citigroup Global Markets Inc. ("Citi") to act as financial advisor to the special committee in connection with its evaluation of the Share Issuance and related transactions. Despite the resulting dilution to our existing stockholders, our Board believes approving the Share Issuance is in our Company's and our stockholders' best interests because our Board believes the restructuring of our contractual arrangements with SNH provides an immediate solution to our liquidity challenges, materially improves the long term financial outlook of our business and further invests SNH in our success.

The Transaction Agreement with SNH and related agreements are included as exhibits to our Current Report on Form 8-K filed with the SEC on April 5, 2019 and are further described elsewhere in this Proxy Statement under the section entitled "Certain Related Person Transactions".

As previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2018 (our "10-K"), we are currently experiencing substantial operating and liquidity challenges, and our management and our independent auditors, RSM US LLP, have determined that, absent the Restructuring Transaction, there is substantial doubt about our ability to continue as a going concern.

Our principal sources of funds to meet our operating and capital expenses and debt service obligations are cash flows from our operating activities, unrestricted cash balances, borrowings under our credit facilities and proceeds from our sales to SNH of certain capital improvements we may make to communities that we lease from SNH. Absent the Restructuring Transaction, we do not expect these sources of funds to be sufficient to meet our ongoing financial obligations. We had an accumulated deficit of $292.6 million at December 31, 2018, we have incurred operating losses in each of the last three years, and we had net negative cash flows from operations of $54.2 million for the year ended December 31, 2018. Further, our existing credit facility is scheduled to mature on June 28, 2019. Without the rent relief resulting from the Restructuring Transaction, we do not believe that our current unrestricted

FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement    15

cash balances would be sufficient to fund our operations and allow us to continue as a going concern. As of the date of this Proxy Statement, we had $51.5 million of borrowings outstanding under our credit facility and had no remaining borrowing availability under that credit facility. Our ability to refinance our credit facility depends, in part, on the lenders' belief that our prospects, operating leverage and expected future operating results will enable us to continue as a going concern. Due to these operating and liquidity challenges, in the absence of the Restructuring Transaction, we do not expect to be able to fund our operating and capital expenses or debt service obligations.

We expect our current financial position to improve and our liquidity challenges to subside if the Share Issuance is approved and the Restructuring Transaction is completed. The Restructuring Transaction was the result of numerous meetings of a special committee of our Board comprised solely of our Independent Directors and its advisors over the past several months. The special committee evaluated multiple options, and engaged in extensive negotiations with the special committee of the board of trustees of SNH, to find a solution that would address our deteriorating financial outlook and liquidity challenges, ranging from the Restructuring Transaction to seeking bankruptcy protection to reorganize our Company. Despite the resulting dilution to our existing stockholders, our Board believes approving the Share Issuance and completing the Restructuring Transaction is in our Company's and our stockholders' best interests because our Board believes the restructuring of our contractual arrangements with SNH provides an immediate solution to our liquidity challenges, materially improves the long term financial outlook of our business and further invests SNH in our success.

A special committee of our Board, comprised solely of our Independent Directors, evaluated a range of options to address our liquidity and operating challenges with the assistance of its advisors, including its legal counsel, Ropes & Gray LLP, and its financial advisor, Citi. The special committee negotiated the Restructuring Transaction with the assistance of its legal and financial advisors. Citi also reviewed with the special committee certain financial aspects of the contribution by SNH to our Company of an aggregate amount of $75.0 million in cash in consideration for the issuance by the Company of up to an aggregate of 262,240,513 Common Shares to SNH and SNH shareholders. The special committee recommended the Restructuring Transaction to the Board, and the Restructuring Transaction was separately approved and adopted by our Independent Directors and the full Board.

The Nasdaq's Listing Rule 5635(b) requires stockholder approval prior to the issuance of securities when the issuance or potential issuance may result in a change of control of the issuer. Under the Nasdaq's rules and policies, a change of control may be deemed to occur when, as a result of an issuance, an investor or a group would own, or have the right to acquire, 20% or more of the outstanding shares of common stock or voting power of the issuer, and such ownership or voting power would be the largest ownership position of the issuer. The Share Issuance will result in SNH owning in excess of 20% of our issued and outstanding Common Shares and obtaining our largest ownership position. Accordingly, the Share Issuance requires stockholder approval Listing Rule 5635(b).

The Nasdaq's Listing Rule 5635(d) requires stockholder approval for a transaction other than a public offering that involves the sale, issuance, or potential issuance by a company of common stock equal to 20% or more of the common stock, or 20% or more of the voting power outstanding before the issuance for less than the lower of (i) the closing price of the Common Shares immediately preceding the signing of the Transaction Agreement or (ii) the average closing price of the Common Shares for the five trading days immediately preceding the signing of the Transaction Agreement (the "Minimum Price"). The Share Issuance to SNH will result in an issuance of up to approximately 199.7% of the Common Shares issued and outstanding before the Share Issuance and the Share Issuance to SNH shareholders will result in an issuance of approximately 311.9% of the Common Shares issued and outstanding before the Share Issuance, subject in each case to adjustment as provided for in the Transaction Agreement. Accordingly, the Share Issuance may be deemed to require stockholder approval under Listing Rule 5635(d) as well, because the consideration to be paid by SNH in connection with the Share Issuance may be deemed to

16    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement

be below the Minimum Price. Stockholder approval of the Share Issuance is a condition to completion of the Restructuring Transaction contemplated by the Transaction Agreement and therefore the issuance of Common Shares to each of SNH and SNH shareholders are being voted upon as a single proposal.

The issuance of up to 262,450,513 Common Shares (as such amount may be adjusted pursuant to the Transaction Agreement) that is the subject of this Item 2, if approved, and the Restructuring Transaction contemplated by the Transaction Agreement if completed, will result in an increase in the number of Common Shares outstanding, and our existing stockholders' ownership of us will be substantially diluted. ABP Trust, which currently beneficially owns approximately 36% of our Common Shares, will own approximately 6% of our Common Shares, after giving effect to the Share Issuance. If the Share Issuance is approved by our stockholders, we will file a registration statement on Form S-1 with the SEC to register the Common Shares to be issued. This Proxy Statement shall not constitute an offer to sell or the solicitation of an offer to buy any Common Shares.

Assuming a quorum is present at the meeting, approval of this Item 2 requires the affirmative vote of a majority of all the votes cast, in person or by proxy, at the 2019 Annual Meeting. SNH and ABP Trust, on behalf of its subsidiary, ABP Acquisition LLC, which collectively beneficially owned approximately 44% of the outstanding Common Shares as of the record date, have each agreed to vote all Common Shares that SNH and ABP Trust beneficially own in favor of approval of the Share Issuance.

If we do not obtain stockholder approval for the Share Issuance by December 31, 2019, SNH may elect to terminate our restructuring arrangement. If such termination occurs, the Transaction Agreement provides that our contractual agreements revert to the terms in effect immediately prior to the execution of the Transaction Agreement. This means that our existing master leases and management agreements and pooling agreements with SNH will be restored in accordance with their terms prior to the Restructuring Transaction and, among other things, we will again be obligated to pay minimum rent under our leases with SNH at the contractual lease rate which, as of the date hereof, is $17.4 million of base rent (which is $6.4 million more per month than the restructured amount). We will also need to repay any amounts owed to SNH under the credit facility it has extended to us and we will not receive the consideration SNH would otherwise have paid for the Share Issuance. If we are not able to consummate the Restructuring Transaction or otherwise renegotiate our arrangements with SNH, we will likely default on our rent obligations owed to SNH and under our credit facilities. If we default on our leases with SNH or either of our credit facilities and do not obtain relief for that default we will be forced to consider other options, including filing for bankruptcy protection and/or ceasing our operations.

The Board of Directors recommends a vote "FOR" the Share Issuance.

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RATIFICATION OF THE APPOINTMENT OF RSM US LLP AS INDEPENDENT AUDITORS (ITEM 3)

Stockholders are voting to ratify the appointment of RSM US LLP as independent auditors of the Company for the Company's fiscal year ending December 31, 2019.

The Audit Committee has the sole authority and responsibility to hire, evaluate and, when appropriate, replace our independent auditors and is directly responsible for the appointment, compensation and general oversight of the work of the independent auditors. The Audit Committee is responsible for approving the audit and permissible non-audit services provided by the independent auditors and the associated fees.

The Audit Committee evaluates the performance of our independent auditors annually and determines whether to reengage the current independent auditors or consider other audit firms. In doing so, the Audit Committee considers the quality and efficiency of the services provided by the auditors, the auditors' technical expertise and knowledge of our operations and industry, the auditors' independence, legal proceedings involving the auditors, the results of PCAOB inspections and peer quality reviews of the auditors and the auditors' reputation in the marketplace. In connection with the mandated rotation of the independent auditors' lead engagement partner, the Audit Committee and its chair consider the selection of the new lead engagement partner identified by the independent auditors.

Based on this evaluation, the Audit Committee has appointed RSM US LLP to serve as the Company's independent auditors for the fiscal year ending December 31, 2019. RSM US LLP has served as the Company's independent auditors since October 6, 2014, and is considered by management and the Audit Committee to be well qualified. Further, the Audit Committee and the Board believe that the continued retention of RSM US LLP to serve as the independent registered public accounting firm is in the best interests of our Company and our stockholders.

The Audit Committee has determined to submit its selection of the independent auditors to the Company's stockholders for ratification. This vote will ratify prior action by the Audit Committee and will not be binding upon the Audit Committee. However, the Audit Committee may reconsider its prior appointment of the independent auditors or consider the results of this vote when it determines to appoint our independent auditors in the future.

The following table shows the fees for audit and other services provided to the Company by RSM US LLP for the fiscal years ended December 31, 2018 and 2017.

18    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement

Audit Fees.    This category includes fees associated with the annual financial statements audit and related audit procedures, work performed in connection with any registration statements and any applicable Current Reports on Form 8-K and the review of any of the Company's Quarterly Reports on Form 10-Q.

Audit Related Fees.    This category consists of services that are reasonably related to the performance of the audit or review of financial statements and are not included in "Audit Fees." These services principally include due diligence in connection with acquisitions, consultation on accounting and internal control matters, audits in connection with proposed or consummated acquisitions, information systems audits and other attest services.

Tax Fees.    This category consists of fees for tax services, including tax compliance, tax advice and tax planning.

All Other Fees.    This category consists of services that are not included in the above categories.

The Audit Committee has established policies and procedures that are intended to control the services provided by our independent auditors and to monitor their continuing independence. Under these policies, no services may be undertaken by our independent auditors unless the engagement is specifically approved by the Audit Committee or the services are included within a category that has been approved by the Audit Committee. The maximum charge for services is established by the Audit Committee when the specific engagement or the category of services is approved. In certain circumstances, our management is required to notify the Audit Committee when approved services are undertaken and the Audit Committee or its Chair may approve amendments or modifications to the engagement or the maximum fees. Our Director of Internal Audit is responsible for reporting to the Audit Committee regarding compliance with these policies and procedures.

The Audit Committee will not approve engagements of the independent auditors to perform non-audit services for the Company if doing so will cause the independent auditors to cease to be independent within the meaning of applicable SEC or the Nasdaq's rules. In other circumstances, the Audit Committee considers, among other things, whether our independent auditors are able to provide the required services in a more or less effective and efficient manner than other available service providers and whether the services are consistent with the Public Company Accounting Oversight Board Rules.

All services for which the Company engaged its independent auditors in 2018 and 2017 were approved by the Audit Committee. The total fees for audit services provided by RSM US LLP in 2018 and 2017 are set forth above and, for 2018, include estimated fee amounts. The Company did not engage RSM US LLP to provide any non-audit services in 2018 or 2017.

The Company has been advised by RSM US LLP that neither the firm, nor any member of the firm, has any material interest, direct or indirect, in any capacity in the Company or its subsidiaries.

One or more representatives of RSM US LLP will be present at the 2019 Annual Meeting. The representatives will have an opportunity to make a statement if they desire to do so and will be available to respond to appropriate questions.

Assuming a quorum is present at the meeting, ratification of the appointment of the independent auditors requires the affirmative vote of a majority of all the votes cast, in person or by proxy, at the 2019 Annual Meeting.

The Board of Directors recommends a vote "FOR" the ratification of the appointment of RSM US LLP as independent auditors.

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DIRECTORS AND EXECUTIVE OFFICERS

The following is some important biographical information, including the ages and recent principal occupations, as of March 15, 2019, of the Company's Director nominee, continuing Directors and executive officers. The business address of the Director nominee, continuing Directors and executive officers is c/o Five Star Senior Living Inc., 400 Centre Street, Newton, Massachusetts 02458. Included in each Director's biography below are the attributes of that Director consistent with the qualifications, attributes, skills and experience the Board has determined are important to be represented on the Board. For a general discussion of the particular Director qualifications, attributes, skills and experience, and the process for selecting and nominating individuals for election to serve as a Director, please see the section entitled "Election of Director" beginning on page 12.

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Director NomineeTable of Contents

Bruce M. Gans, M.D.

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12    FIVE STAR SENIOR LIVING INC. 2020 Proxy Statement

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Bruce M. Gans, M.D.

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​​​ ​​​​ ​​ ​  ​​​​​​​​ ​  ​​ ​​​​ ​​ ​

24    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement

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Adam D. Portnoy

Managing Director since 2018 Group/Term: Class II with a term expiring at the 2020 annual meeting of stockholders Age: 48 Other Public Company Boards: Hospitality Properties Trust (since 2007); Senior Housing Properties Trust (since 2007); Office Properties Income Trust (formerly known as Government Properties Income Trust, since 2009); RMR Real Estate Income Fund, including its predecessor funds (since 2009); The RMR Group Inc. (since 2015); Industrial Logistics Properties Trust (since 2017); Tremont Mortgage Trust (since 2017); TravelCenters of America LLC (since 2018) Mr. Portnoy has been the president and chief executive officer of The RMR Group Inc. ("RMR Inc.") since shortly after its formation in 2015. Mr. Portnoy has been the president and chief executive officer of RMR LLC since 2005 and was a director of RMR LLC from 2006 until June 5, 2015 when RMR LLC became a majority owned subsidiary of RMR Inc. and RMR Inc. became RMR LLC's managing member. Mr. Portnoy has been a director of RMR Advisors LLC since 2007 and served as its president from 2007 to September 2017 and its chief executive officer from 2015 to September 2017. Mr. Portnoy has been a director of Tremont Realty Advisors LLC since March 2016, and served as its president and chief executive officer from March 2016 through December 2017. Mr. Portnoy is an owner, the sole trustee and an officer of ABP Trust. Mr. Portnoy is the majority owner and has been a director of Sonesta International Hotels Corporation since 2012. Mr. Portnoy served as president and chief executive officer of RMR Real Estate Income Fund from 2007 to 2015 and as president of Office Properties Income Trust from 2009 to 2011. Mr. Portnoy was a managing trustee of Select Income REIT from 2011 until it merged with a wholly owned subsidiary of Office Properties Income Trust in December 2018. Mr. Portnoy was a managing trustee of Equity Commonwealth from 2006 until 2014 and served as its president from 2011 to 2014. Prior to joining RMR LLC in 2003, Mr. Portnoy held various positions in the finance industry and public sector, including working as an investment banker at Donaldson, Lufkin & Jenrette and working in private equity at DLJ Merchant Banking Partners and at the International Finance Corporation (a member of The World Bank Group). In addition, Mr. Portnoy previously founded and served as chief executive officer of a privately financed telecommunications company. Mr. Portnoy currently serves as the Honorary Consul General of the Republic of Bulgaria to Massachusetts and on the Board of Directors of Pioneer Institute, and previously served on the board of governors for the National Association of Real Estate Investment Trusts and the board of trustees of Occidental College. Specific Qualifications, Attributes, Skills and Experience: • extensive experience in, and knowledge of, the CRE industry; • leadership position with RMR LLC and demonstrated management ability; • knowledge of the Company's businesses and industries; • public company trustee and director service; • experience in investment banking and private equity; • experience in starting a telecommunications company and serving as its senior executive; • institutional knowledge earned through prior service on the Board and in leadership positions with RMR LLC; and • qualifying as a Managing Director in accordance with the requirements of our Bylaws. The Nominating and Governance Committee and the Board believe that, because Mr. Portnoy is the president and chief executive officer of RMR LLC, his day to day work requires his extensive attention to the business of all the companies for which he serves as a managing trustee or managing director, including the Company, and therefore, service on these additional boards does not impair the amount of attention or time that Mr. Portnoy spends on service on our Board. The Board believes that Mr. Portnoy's extensive familiarity with the day to day business of the Company provides valuable insight for the Board.

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Independent Director since 2001 Group/Term: Group III with a term expiring at the 2022 annual meeting of stockholders Age: 73 Board Committees: Audit; Compensation (Chair); Nominating and Governance; Quality of Care (Chair) Other RMR Managed Public Company Boards: • Industrial Logistics Properties Trust (since 2018) Other Non-RMR Managed Public Company Boards: None

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Dr. Gans has been executive vice president and chief medical officer at the Kessler Institute for Rehabilitation since 2001 and national medical director for Rehabilitation Select Medical, the parent company of the Kessler Institute, since 2003. He is also a professor of physical medicine and rehabilitation at Rutgers University—New Jersey Medical School. Dr. Gans was an independent trustee of Service Properties Trust from 2009 until 2015. Dr. Gans has also served as president and chief executive officer of the Rehabilitation Institute of Michigan. In Dr. Gans's extensive academic career, he has served as professor of physical medicine and rehabilitation at a number of universities, in addition to his current position at Rutgers University—New Jersey Medical School. Dr. Gans is editor of a standard medical textbook on physical medicine and rehabilitation, which is now in its fifth edition, and he has written or coauthored more than forty articles in peer-reviewed publications and twenty-eight abstracts and has served on editorial boards for many medical journals, including serving as the associate editor of the American Journal of Physical Medicine and Rehabilitation. Dr. Gans has testified before the Senate Committee on Veterans' Affairs and has been called on to serve on technical expert panels and to advise the Medicare Payment Advisory Commission, the independent congressional agency established in 1997 to advise the U.S. Congress on issues affecting the Medicare program. Dr. Gans has also served as president of the American Academy of Physical Medicine and Rehabilitation, a medical society with more than 7,500 members, and as a leader in numerous other professional organizations. Specific Qualifications, Attributes, Skills and Experience: • Demonstrated leadership capability, including through his service in many healthcare management, professional, academic and civic leadership positions; • Business experience as the chief executive of a large medical organization; • Extensive experience in, and knowledge of, the healthcare industry and healthcare public policy matters; • Work on public company boards and board committees; • Many academic and professional achievements; • Institutional knowledge earned through prior service on our Board; and • Qualifying as an Independent Director in accordance with the requirements of the Nasdaq, the SEC and our Bylaws.

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FIVE STAR SENIOR LIVING INC. 2020 Proxy Statement    13

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14    FIVE STAR SENIOR LIVING INC. 2020 Proxy Statement    25

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The Company's executive officers serve at the discretion of our Board. There are no family relationships among any of the Company's Directors or executive officers.

	​	Katherine E. Potter President and Chief Executive Officer since 2019 Age: 43 Ms. Potter previously served as the Company's Executive Vice President and General Counsel in 2018 and Senior Vice President and General Counsel from 2016 to 2018 and, prior to that as Vice President and General Counsel from 2012 to 2016. Ms. Potter has practiced law for over ten years, focusing on corporate, securities, mergers and acquisitions, corporate governance and other transactional matters. Ms. Potter was an associate at the law firm of Sullivan & Worcester LLP from 2005 to 2011, and was an attorney at the law firm of Burns & Levinson LLP from 2011 to 2012. ​
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	​	Richard A. Doyle, Jr. ​ ​ Executive Vice President since 2018 Chief Financial Officer and Treasurer since 2016 Age: 50 Mr. Doyle previously served as the Company's Senior Vice President from 2016 to 2018. Mr. Doyle has been a senior vice president of RMR LLC since 2007. Mr. Doyle served as chief financial officer and treasurer of Senior Housing Properties Trust from 2007 through 2015. He previously served as the Company's Director of Financial Reporting from 2005 to 2006. Mr. Doyle holds an MBA degree and is a certified public accountant. There are no family relationships among any of the Company's Directors or executive officers. The Company's executive officers serve at the discretion of the Board. ​ 26    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement ​ Director Nominations The Nominating and Governance Committee is responsible for identifying and evaluating nominees for Director and for recommending to the Board nominees for election at each annual meeting of stockholders. The Nominating and Governance Committee may consider candidates suggested by the Company's Directors, officers or stockholders or by others. Stockholder Recommendations for Nominees.  Stockholders who would like to recommend a nominee for the position of Director should submit their recommendations in writing by mail to the Chair of the Nominating and Governance Committee, c/o Five Star Senior Living Inc., Secretary, at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458 or by email to secretary@5ssl.com. A stockholder's recommendation should include any information that the recommending stockholder believes relevant to the Nominating and Governance Committee's consideration. The Nominating and Governance Committee may request additional information about the stockholder recommended nominee or about the stockholder recommending the nominee. Recommendations by stockholders will be considered by the Nominating and Governance Committee in its discretion using the same criteria as other candidates it considers. Stockholder Nominations for Directors.  Our Bylaws also provide that a stockholder of the Company may nominate a person for election to the Board provided the stockholder complies with the advance notice provisions set forth in our Bylaws, which include, among other things, requirements as to the proposing stockholder's timely delivery of advance notice, continuous requisite ownership of Common Shares and submission of specified documentation and information. For more information on how stockholders can nominate Directors for election to the Board, see "Stockholder Nominations and Other Proposals" beginning on page 37. DIRECTOR COMPENSATION The Compensation Committee is responsible for reviewing and determining the Common Share awards granted to Directors and making recommendations to the Board regarding cash compensation paid to Directors, in each case, for Board, committee and committee chair services. Managing Directors do not receive cash compensation for their services as Directors but do receive Common Share awards for their Board service. The number of Common Shares awarded to each Managing Director for Board service is the same as the number awarded to each Independent Director. Director Share Ownership Guidelines The Board believes it is important to align the interests of Directors with those of our stockholders, and for Directors to hold equity ownership positions in the Company. Accordingly, each Director is expected to hold at least 50,000 Common Shares by the later of: (i) the date of the 2019 Annual Meeting and (ii) five years from the annual meeting of stockholders of the Company at which the Director was initially elected or, if earlier, the first annual meeting of stockholders of the Company following the initial election of the Director to the Board. Compliance with these ownership guidelines is measured as of the end of each fiscal year. Any Director who is prohibited by law or by applicable regulation of his or her employer from owning equity in the Company is exempt from this requirement. The Nominating and Governance Committee may consider whether exceptions should be made for any Director on whom this requirement could impose a financial hardship. As of March 15, 2019, all Directors have met or, within the applicable period, are expected to meet, these share ownership guidelines. ​ FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement    27 2018 Annual Director Compensation In 2018, each Independent Director received an annual fee of $40,000 for services as a Director, plus a fee of $1,250 for each meeting attended. Up to two $1,250 fees were paid if a Board meeting and one or more Board committee meetings, or two or more Board committee meetings, were held on the same date. Each Independent Director and Managing Director received an annual award of 12,500 Common Shares in 2018. Each Independent Director who served as a committee chair of the Board's Audit, Quality of Care, Compensation or Nominating and Governance Committees received an additional annual fee of $20,000, $20,000, $10,000 and $10,000, respectively. Directors were reimbursed for travel expenses they incurred in connection with their duties as Directors and for out of pocket costs they incurred in connection with their attending certain continuing education programs. The following table details the total compensation of the Directors for the year ended December 31, 2018 for services as a Director. Name   Fees Earned or Paid in Cash ($)(1)   Stock Awards ($)(2)   All Other Compensation ($)   Total ($)   ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Donna D. Fraiche   $ 72,500   $ 14,375   $ —   $ 86,875   Bruce M. Gans, M.D.     93,750     14,375     —     108,125   Barbara D. Gilmore   ​ 82,500   ​ 14,375   ​ —   ​ 96,875   Gerard M. Martin(3)     —     14,375     —     14,375   Barry M. Portnoy(3)(4)   ​ —   ​ —   ​ —   ​ —   Adam D. Portnoy(3)(4)     —     31,250     —     31,250   ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) The amounts reported in the Fees Earned or Paid in Cash column reflect the cash fees earned by each Independent Director in 2018, consisting of a $40,000 annual cash fee and each of Ms. Fraiche, Dr. Gans and Ms. Gilmore earned an additional $10,000, $30,000 and $20,000, respectively, for service as a committee chair in 2018. Ms. Fraiche, Dr. Gans and Ms. Gilmore earned an additional $22,500, $23,750 and $22,500, respectively, in fees for meetings attended in 2018. (2) Equals 12,500 Common Shares multiplied by the closing price of such shares on May 17, 2018, the award date, and for Adam Portnoy includes an additional 12,500 Common Shares multiplied by the closing price of such shares on March 20, 2018, the award date for Common Shares awarded in connection with his initial election as a Managing Director. Amounts shown are also the compensation cost for the award recognized by the Company for financial reporting purposes pursuant to Financial Accounting Standards Board Accounting Standards Codification Topic 718, "Compensation—Stock Compensation" ("ASC 718") (which equals the closing price of the shares on the award date, multiplied by the number of shares subject to the grant). No assumptions were used in this calculation. All Common Share awards fully vested on the award dates. (3) Managing Directors do not receive cash compensation for their services as Directors. (4) Mr. Barry Portnoy served as a Managing Director of the Company until his death on February 25, 2018. The Board elected Mr. Adam Portnoy as a Managing Trustee effective March 20, 2018. ​ 28    FIVE STAR SENIOR LIVING INC. 2019 Proxy Statement ​ CORPORATE GOVERNANCE The Board is committed to corporate governance that promotes the long term interests of our stockholders. The Board has established Governance Guidelines that provide a framework for effective governance. The guidelines address matters such as general qualification standards for the Board, Director responsibilities, Board meetings and communications, Board committees, Director access to management and independent advisers, Director compensation and share ownership guidelines, Director orientation and continuing education, executive development and succession planning, related person transactions, annual performance evaluation of the Board and other matters. The Board regularly reviews developments in corporate governance and updates our Governance Guidelines and other governance materials as it deems necessary and appropriate. The governance section of our website makes available our corporate governance materials, including the Governance Guidelines, the charter for each Board committee, and the Code. To access these documents on the Company's website,www.fivestarseniorliving.com, click on "Investor Relations" and then click on "Corporate Governance." In addition, instructions on how to obtain copies of the Company's corporate governance materials are included in the response toquestion 17 in the "Questions and Answers" section on page 11. Board Leadership Structure In accordance with our Charter and Bylaws, the Board comprises five Directors, including three Independent Directors and two Managing Directors. All Directors play an active role in overseeing the Company's business both at the Board and committee levels. As set forth in the Company's Governance Guidelines, the core responsibility of our Directors is to exercise sound, informed and independent business judgment in overseeing the Company and its strategic direction. Our Directors are skilled and experienced leaders and currently serve or have served as members of senior management in public and private for profit organizations and law firms, and have also served in academia. Our Directors may be called upon to provide solutions to various complex issues and are expected to, and do, ask hard questions of the Company's officers and advisors. The Board is small, which facilitates informal discussions and communication from management to the Board and among Directors. We do not have a Chairman of the Board or a lead Independent Director. Our President and Chief Executive Officer since 2019 Age: 44 Ms. Potter previously served as the Company's Executive Vice President and General Counsel in 2018 and Senior Vice President and General Counsel from 2016 to 2018 and, prior to that as Vice President and General Counsel from 2012 to 2016. Ms. Potter also serves as a senior vice president of RMR LLC since 2018 and prior to that served as a vice president of RMR LLC since 2016. Ms. Potter has practiced law for over ten years, focusing on corporate, securities, mergers and acquisitions, corporate governance and other transactional matters. Ms. Potter was an associate at the law firm of Sullivan & Worcester LLP from 2005 to 2011, and was an attorney at the law firm of Burns & Levinson LLP from 2011 to 2012.	​
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