Statement of Changes in Beneficial Ownership (4)

FORM 4

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

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3235-0287

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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * ADVENT INTERNATIONAL CORP/MA	2. Issuer Name and Ticker or Trading Symbol Syneos Health, Inc. [ SYNH ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                    __X__ 10% Owner _____ Officer (give title below)    _____ Other (specify below)
(Last)          (First)          (Middle) PRUDENTIAL TOWER, 800 BOYLSTON STREET, SUITE 3300	3. Date of Earliest Transaction (MM/DD/YYYY) 3/3/2021
(Street) BOSTON, MA 02199-8069 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _ X _ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. Code (Instr. 8)		4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Class A Common Stock	3/3/2021		S(1)		4331222 (1)	D	$74.175	11087573	I	See Notes (4)(5)
Class A Common Stock	3/3/2021		S(3)		322824 (2)	D	$74.175	10764749 (3)	I	See Notes (4)(5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:
(1)	See Exhibit 99.1 for text of footnote (1).
(2)	See Exhibit 99.1 for text of footnote (2).
(3)	See Exhibit 99.1 for text of footnote (3).
(4)	See Exhibit 99.1 for text of footnote (4).
(5)	See Exhibit 99.1 for text of footnote (5).

Remarks: Exhibit 99.1 (Footnotes to Form 4) and Exhibit 99.2 (Signatures and Joint Filer Information) are incorporated herein by reference. This Form 4 is the first of six Form 4s being filed relating to the same event. This Form 4 has been split into six filings because there are more than 10 Reporting Persons in total, and the SEC's EDGAR filing system limits a single Form 4 to a maximum of 10. Each part will be filed by Designated Filer, Advent International Corporation.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
ADVENT INTERNATIONAL CORP/MA PRUDENTIAL TOWER, 800 BOYLSTON STREET SUITE 3300 BOSTON, MA 02199-8069		X
Double Eagle Investor Holdings, L.P. C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
Double Eagle GP, LLC C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
Advent International GPE VIII-C Limited Partnership C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
GPE VIII GP S.a.r.l. C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
GPE VIII GP Limited Partnership C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
Advent International GPE VIII, LLC C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
GPE VII GP S.a.r.l. C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
GPE VII GP Limited Partnership C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X
Advent International GPE VII, LLC C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET, SUITE 3300 BOSTON, MA 02199-8069		X

Signatures
See Exhibit 99.2		3/5/2021
**Signature of Reporting Person		Date