LIMITED POWER OF ATTORNEY

        The undersigned hereby constitutes and appoints each of Geoff MacKay,
Katina Dorton, and Arthur R. McGivern, signing singly, and with full power of
substitution, the undersigned's true and lawful attorney-in-fact to:

        (1)   execute for and on behalf of the undersigned, in the undersigned's
capacity as officer and/or director of AVROBIO, Inc. (the "Company"), from time
to time the following U.S. Securities and Exchange Commission ("SEC") forms: (i)
Form ID, including any attached documents (such as Update Passphrase
Authentication), to effect the assignment of codes to the undersigned to be used
in the transmission of information to the SEC using the EDGAR System; (ii) Form
3, Initial Statement of Beneficial Ownership of Securities, including any
attached documents; (iii) Form 4, Statement of Changes in Beneficial Ownership
of Securities, including any attached documents; (iv) Form 5, Annual Statement
of Beneficial Ownership of Securities in accordance with Section 16(a) of the
Securities Exchange Act of 1934, as amended, and the rules thereunder, including
any attached documents; (v) Schedules 13D and 13G and (vi) amendments of each
thereof, in accordance with the Securities Exchange Act of 1934, as amended, and
the rules thereunder, including any attached documents;

        (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
Form 3, 4 or 5, Schedules 13D and 13G or any amendment(s) thereto, and timely
file such form(s) with the SEC and any securities exchange, national association
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 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 and thing
whatsoever requisite, necessary or proper 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 such
attorney-in-fact, or 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 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 16 or Regulation 13D-G of
the Securities Exchange Act of 1934, as amended.  The undersigned hereby agrees
to indemnify the attorneys- 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 the attorneys-in-fact.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file such forms 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.  This Power of Attorney supersedes any prior power
of attorney in connection with the undersigned's capacity as an officer and/or
director of the Company.  This Power of Attorney shall expire as to any
individual attorney-in-fact if such attorney-in-fact ceases to be an executive
officer of, or legal counsel to, the Company.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of June 10, 2018.

                                        /s/ Phillip Donenberg
                                        ------------------------------
                                        Phillip Donenberg