POWER OF ATTORNEY

Known all by these presents, that the undersigned hereby constitutes and
appoints each of Jonathan Olefson, Jason Meggs and Sara Epstein, and each of
them acting alone, signing singly, 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 an officer, director and/or 10% or more stockholder of
Syneos Health, Inc. (the "Company"), Forms ID, 3, 4, 5 and Update Passphrase
Acknowledgement (and any amendments thereto) in accordance with Section 16(a) of
the Securities Exchange Act of 1934, as amended (the "1934 Act"), and the rules
promulgated 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 Form ID, 3, 4, 5 and Update Passphrase Acknowledgement (and any amendments
thereto) and to file timely such form 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 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 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 of the 1934 Act.

This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms ID, 3, 4 and 5 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 each of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 15th day of November 2019.

/s/ Alistair Macdonald
Alistair Macdonald