Argo Group International (ARGO-PA) 10-Q 2013 Q1 Quarterly report

Exhibit 32.1

Certification of CEO 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 Quarterly Report on Form 10-Q of Argo Group International Holdings, Ltd. (the “Company”) for the quarterly period ended March 31, 2013 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), Mark E. Watson III, as President and Chief Executive Officer of the Company, hereby certifies, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that, to the best of his knowledge:

1. 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.

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Certified this 9^th day of May 2013.

/s/ Mark E. Watson III

Mark E. Watson III

President and Chief Executive Officer