GAIN Capital 10-K 2015 FY Annual report

Exhibit 32.2

CERTIFICATION OF CHIEF FINANCIAL OFFICER,

AS REQUIRED BY SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, Nigel Rose, the undersigned Chief Financial Officer of GAIN Capital Holdings, Inc., a Delaware corporation (the “Company”), hereby certify pursuant to 18 U.S.C. Section 1350 as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 that to my knowledge:

1. The accompanying annual report on Form 10-K for the fiscal year ended December 31, 2015 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

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

Date: March 17, 2016

/s/ Nigel Rose

Nigel Rose

Chief Financial Officer

(Principal Financial and Accounting Officer)

A signed original of this written statement required by Section 906, or other document authenticating, acknowledging, or otherwise adopting the signature that appears in typed form within the electronic version of this written statement required by Section 906, has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.