PMX Agency is Stagwell's fourth acquisition since October 2015. The holding company's other agencies include National Research Group, political consulting firm SKDKnickerbocker and creative digital agency Code and Theory, which it bought in January.
"We continue to fill in the marketing wheel," said Mr. Penn. "We have a great digital agency in Code and Theory, public affairs with SKDKnickerbocker and research with NRG, so this is another piece of the puzzle for us."
PMX Agency, with clients such as The North Face, the American Heart Association and Dow Jones, specializes in direct-response marketing, which is "powerful for retailers and people trying to sell their products online or in physical stores," said Mr. Penn.
Chris Paradysz and Mike Cousineau, co-CEOs at PMX Agency, will continue in their roles, and the shop will operate independently within Stagwell. Mr. Paradysz and Mr. Cousineau will report directly to Mr. Penn.
Mr. Penn added that he's still "intensely looking" at analytics, media buying and TV advertising agencies, among other areas of specialty.
With its acquisition of PMX Agency, which has 300 staffers, Stagwell Group's overall headcount is about 850, said Mr. Penn. By the end of the year, Mr. Penn said he expects revenue from the four agencies within the group to be about $200 million.
Global financial services firm BTIG advised PMX Agency throughout the process. Financial terms of the deal were not disclosed.