Sec Form 4 Filing - ADVENT INTERNATIONAL CORP/MA @ Party City Holdco Inc. - 2017-12-22

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 Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person ADVENT INTERNATIONAL CORP/MA 2. Issuer Name and Ticker or Trading Symbol Party City Holdco Inc. [ PRTY] 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) 800 BOYLSTON STREET, 3. Date of Earliest Transaction (MM/DD/YY) 12/22/2017 (Street) BOSTON, MA02199 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction 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 Common Stock 12/22/2017 S 19,841,694 ( 1 ) D $ 12.2 0 I See Notes ( 2 ) ( 3 ) ( 4 ) ( 5 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ADVENT INTERNATIONAL CORP/MA 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-A LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-B LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-C LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-D LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-E LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-F LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X ADVENT INTERNATIONAL GPE VI-G LP C/O ADVENT INTERNATIONAL CORPORATION 800 BOYLSTON STREET BOSTON, MA02199 X Signatures /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date /s/ Richard Terranova, Attorney-in-Fact 12/27/2017 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of common stock of the Issuer were sold in connection with a stock purchase agreement by and between the Issuer and the Advent-Party City Acquisition Limited Partnership ("ACPA") pursuant to which the Issuer repurchased the shares. Following the repurchase, ACPA no longer holds any shares of the Issuer. ( 2 )APCA directly held the shares of common stock of the Issuer prior to the transaction being reported. The Advent Funds (as defined below) directly own all of the partnership interests in APCA. APCA, together with Advent International Corporation ("AIC"), Advent International LLC ("AILLC"), GPE VI GP Limited Partnership ("GPE VI"), GPE VI GP (Delaware) Limited Partnership ("GPE VI D") and the Advent Funds, are referred to herein as the "Reporting Persons". ( 3 )AIC is the manager of AILLC, which is the general partner of each of GPE VI, GPE VI D, Advent Partners GPE VI 2008 Limited Partnership ("GPE 2008), Advent Partners GPE VI 2009 Limited Partnership ("GPE 2009"), Advent Partners GPE VI 2010 Limited Partnership ("GPE 2010"), Advent Partners GPE VI-A Limited Partnership ("GPE A"), and Advent Partners GPE VI-A 2010 Limited Partnership ("GPE A 2010", together with GPE 2008, GPE 2009, GPE 2010 and GPE A, collectively, the "Advent Partner Entities"). ( 4 )GPE VI D is the general partner of the following entities: Advent International GPE VI-C Limited Partnership, Advent International GPE VI-D Limited Partnership and GPE VI-E Limited Partnership (collectively, the "GPE VI D Funds"). ( 5 )GPE VI is the general partner of the following entities: Advent International GPE VI-G Limited Partnership, Advent International GPE VI Limited Partnership, Advent International GPE VI-A Limited Partnership, Advent Internal GPE VI-B Limited Partnership, and Advent International GPE VI-F Limited Partnership (collectively, the "GPE VI Funds" and together with the GPE VI D Funds and the Advent Partner Entities, collectively the "Advent Funds").

Remarks: This Form 4 is the first of two Forms 4 being filed relating to the same event. The Form 4 has been split into two 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 Reporting Persons. Each Form 4 will be filed by Designated Filer Advent International Corporation.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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