Exhibit 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Each of Michael D. Clayman, M.D., President and Chief Executive Officer of Flexion Therapeutics, Inc. (the “Registrant”), and David A. Arkowitz, Chief Financial Officer of the Registrant, do hereby certify in accordance with 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, based upon our knowledge:

(1) this Quarterly Report on Form 10-Q of the Registrant, to which this certification is attached as an exhibit (the “Report”), fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m); and

(2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

Date: August 5, 2020	/s/ Michael D. Clayman, M.D.
	Michael D. Clayman, M.D.
	President and Chief Executive Officer
Date: August 5, 2020	/s/ David A. Arkowitz
	David A. Arkowitz
	Principal Financial and Accounting Officer

The foregoing certification is being furnished solely pursuant to 18 U.S.C. Section 1350 and is not being filed as part of the Report or as a separate disclosure document.