The Hanover Insurance Group, Inc. (THG) 10-Q 2015 Q3 Quarterly report

Exhibit 32.1

CERTIFICATION PURSUANT TO

SECTION 1350, CHAPTER 63 OF TITLE 18, UNITED STATES CODE,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Pursuant to Section 1350, Chapter 63 of Title 18, United States Code, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned, as President, Chief Executive Officer, Director and Acting Chief Financial Officer of The Hanover Insurance Group, Inc. (the “Company”), does hereby certify that to the undersigned’s knowledge:

1)the Company’s Quarterly Report on Form 10-Q for the period ended September 30, 2015 (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 Company’s Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Frederick H. Eppinger, Jr.

Frederick H. Eppinger, Jr.

President, Chief Executive Officer, Director and Acting Chief Financial Officer (Principal Financial Officer)

Dated: October 30, 2015