LIMITED POWER OF ATTORNEY

The undersigned hereby constitutes and appoints each of Jason F. Cole,
Jeffrey T. Walsh, Kory Wentworth, and Helen Fu, and each of them individually,
and with full power of substitution, the
undersigned's true and lawful attorney-in-fact to:

     (1)     Complete and execute for and on behalf of the undersigned, in the
             undersigned's capacity as an officer, director and/or ten percent
             (10%) shareholder of bluebird bio, Inc., a Delaware corporation
             (the "Company") any and all instruments, certificates and documents
             required to be executed on behalf of the undersigned as an
             individual or on behalf of the undersigned's company or
             partnership, as the case may be, pursuant to Section 13 and Section
             16 of the Securities Exchange Act of 1934, as amended (the
             "Exchange Act") or the rules and regulations thereunder;

     (2)     Do and perform any and all acts for and on behalf of the
             undersigned which may be necessary or desirable to complete and
             execute any such instruments, certificates or documents required to
             be filed pursuant to Sections 13 and 16 of the Exchange Act or the
             rules or regulations thereunder and timely file such forms with the
             United States Securities and Exchange Commission and any stock
             exchange or similar authority; and


     (3)     Take any other action of any type whatsoever in connection with the
             foregoing which, in the opinion of such attorney-in-fact, may be of
             benefit to, in the best interest of, or legally required by, the
             undersigned, it being understood that the documents executed by any
             such attorney-in-fact on behalf of the undersigned pursuant to this
             Power of Attorney shall be in such form and shall contain such
             terms and conditions as such attorney-in-fact may approve in such
             attorney-in-fact's discretion.

     The undersigned hereby grants to each such attorney-in-fact, acting singly,
full power and authority to do and perform any and every act which is necessary,
proper or desirable to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that any such attorney-in-fact, or any such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this Power of Attorney and the rights and powers herein
granted.

      The undersigned acknowledges that each of the foregoing attorneys-in-fact,
in serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 13 or Section 16 of the Exchange Act or the rules or regulations
thereunder.  The undersigned hereby agrees to indemnify each attorney-in-fact
and the Company from and against any demand, damage, loss, cost or expense
arising from any false or misleading information provided by the undersigned to
such attorney-in fact.

     This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file any instruments, certificates and
documents pursuant to Section 13 and 16 of the Exchange Act or the rules or
regulations thereunder with respect to the undersigned's holdings of and
transactions in securities issued by the Company, unless earlier revoked by the
undersigned in a signed writing delivered to the foregoing attorneys-in-fact.

	IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 7, 2018.

                          /s/ Mark Vachon
                              Mark Vachon