Exhibit 32.1

CERTIFICATIONS PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906 OF

THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report on Form 10-K of FTS International, Inc. (the “Company”) for the fiscal year ending December 31, 2018, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned, Michael J. Doss, Chief Executive Officer of the Company, and Lance D. Turner, Chief Financial Officer and Treasurer of the Company, each certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 that:

1. The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of the dates and for the periods indicated.

Date: February 28, 2019	By:	/s/ Michael J. Doss
		Michael J. Doss
		Chief Executive Officer and Director (Principal Executive Officer)
Date: February 28, 2019	By:	/s/ Lance D. Turner
		Lance D. Turner
		Chief Financial Officer and Treasurer (Principal Financial Officer and Principal Accounting Officer)