bluebird bio (BLUE) 10-Q 2015 Q2 Quarterly report

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 Quarterly Report on Form 10-Q of bluebird bio, Inc. (the “Company”) for the period ended June 30, 2015 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned officers of the Company hereby certifies, pursuant to 18 U.S.C. Section 1350, that to his or her knowledge:

(1) the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

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

Date: August 6, 2015	By:	/s/ Nick Leschly
		Nick Leschly President, Chief Executive Officer and Director (Principal Executive Officer and Duly Authorized Officer)
Date: August 6, 2015	By:	/s/ James M. DeTore
		James M. DeTore Chief Financial Officer and Treasurer (Principal Financial Officer and Duly Authorized Officer)