The agency won the business after a shoot-out against Fred Farid Lambert, following a five-month pitch process, which was handled by Agency Assessments International.
M&C Saatchi will work on Jameson's communications on a global basis, excluding the US. BDH\TBWA was the last UK agency to do any Jameson above-the-line work.
Wieden & Kennedy Amsterdam and BDH\TBWA were knocked out of the pitch earlier this year.
The review comes as Jameson plans to increase its global spend on advertising and promotions to £34 million.
M&C Saatchi declined to comment. Jameson denied a decision had been made.