UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

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Flexion Therapeutics, Inc.

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flexion Transformative Medicine ... Where It Matters Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders To Be Held on June 19, 2019 for Flexion Therapeutics, Inc. This communication is not a form of voting and presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. To view the proxy statement, annual report, directions to the annual meeting and voting instructions, go to www.proxydocs.com/FLXN. To submit your proxy while visiting this site, you will need the 12 digit control number in the box below. Under United States Securities and Exchange I I Commission rules, proxy materials do not have to be delivered in paper. Proxy materials can be distributed by making them available on the Internet. We have chosen to use these procedures for our 2019 Annual Meeting and need YOUR participation. L _j If you want to receive a paper or e-mail copy of the proxy materials, you must request one. There is no charge to you for requesting a copy. In order to receive a paper package in time for our Annual Meeting, please make this request on or before June 10, 2019. For a Convenient Way to VIEW Proxy Materials -and- VOTE Online go to: www.proxydocs.com/FLXN Proxy Materials Available to View or Receive: Annual Report and Proxy Statement Printed materials may be requested by one of the following methods: INTERNET www.investorelections.com/FLXN r::r.=o L::J TELEPHONE (866} 648-8133 You must use the 12 digit control number located in the shaded gray box below. I *E-MAIL paper@investorelections.com * If requesting material by e-mail, please send a blank email with the 12 digit control number (located below) in the subject line. No other requests, instructions or other inquiries should be included with your e-mail requesting material. Flexion Therapeutics, Inc. Notice of Annual Meeting Meeting Type: Annual Meeting f I e x i 0 n For holders as of: April 22, 2019 Date: Wednesday, June 19, 2019 ~ Transformative Medicine... Time: 1:30 P.M. (Eastern Time) Where it Matters Place: Marriott Hotel, 1 Burlington Mall Road, Burlington, MA 01803 The Board of Directors Recommends a Vote FOR each of the director nominees listed in proposal 1, FOR proposal 2, FOR proposal 3, and for the "1 year" option for proposal 4. 1. To elect three Class II directors to hold office until the 2022 annual meeting of stockholders. Nominees: (01) Scott A. Canute (02) Samuel D. Colella (03) Mark P. Stejbach 2. To ratify the selection of PricewaterhouseCoopers LLP as the Company's independent registered public accounting firm for its fiscal year ending December 31, 2019. 3. To approve, on an advisory basis, the compensation of the Company's named executive officers. 4. To indicate, on an advisory basis, the preferred frequency of stockholder advisory votes on the compensation of the Company's named executive officers. Note: To conduct any other business properly brought before the Annual Meeting. Vote In-Person Instructions: While we encourage stockholders to vote by the means indicated above, a stockholder is entitled to vote in person at the Annual Meeting. If you wish to vote your shares at the Annual Meeting, please register with the Inspector of Elections at the desk marked "Stockholder Registration" at the entrance to receive a ballot. Proper photo ID is required. Ballots should be returned to the Inspector of Elections in order to be counted. Additionally, a stockholder who has submitted a proxy before the meeting may revoke that proxy in person at the Annual Meeting.