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

In connection with the Annual Report on Form 10-K of Zafgen, Inc. (the “Company”) for the period ended December 31, 2017, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned officers hereby certify, pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, 18 U.S.C. Section 1350, that to his or her knowledge:

1) the Report which this statement accompanies fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

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

Dated: March 9, 2018	/s/ Jeffrey Hatfield
	Jeffrey Hatfield
	Chief Executive Officer
	(Principal Executive Officer)
Dated: March 9, 2018	/s/ Patricia Allen
	Patricia Allen
	Chief Financial Officer
	(Principal Financial and Accounting Officer)