UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

Current Report

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of Earliest Event Reported): May 15, 2018

Party City Holdco Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (914) 345-2020

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Indicate by check mark whether the registrant is an emerging growth company as defined in as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company  ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

On May 15, 2018, Party City Holdco Inc. (the “Company”) entered into an Underwriting Agreement (the “Underwriting Agreement”) with Morgan Stanley & Co. LLC (the “Underwriter”) and THL PC Topco, L.P. (the “Selling Stockholder”), relating to the underwritten offering of 12,000,000 shares (the “Shares”) of the Company’s common stock, par value $0.01 per share (the “Offering”). All of the Shares are being sold by the Selling Stockholder. The Underwriter has agreed to purchase the Shares from the Selling Stockholder pursuant to the Underwriting Agreement at a price of $15.00 per share.

The Offering is being made only by means of a prospectus. A shelf registration statement (including a prospectus) relating to the offering of common stock was filed with the Securities and Exchange Commission (“SEC”) on September 2, 2016, and became effective on September 30, 2016 (Registration No. 333-213492) (the “Registration Statement”). A prospectus supplement relating to the Offering was filed with the SEC on May 15, 2018. The closing of the Offering is expected to take place on May 18, 2018, subject to the satisfaction of customary closing conditions. A copy of the Underwriting Agreement is filed as Exhibit 1.1 to this Current Report on Form 8-K.

Ropes & Gray LLP, counsel to the Company, has issued an opinion to the Company, dated May 17, 2018, regarding the Shares to be sold in the Offering. A copy of the opinion is filed as Exhibit 5.1 to this Current Report on Form 8-K. Certain information relating to Part II, Item 14 “Other Expenses of Issuance and Distribution” of the Registration Statement is filed as Exhibit 99.1 to this Current Report on Form 8-K.

(d) Exhibits

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: May 17, 2018