Terms of the deal were not disclosed, but it is reported that it is a non-cash acquisition and that senior executives at Media First will have earn-outs.
Last year, Media First managed $330m (£226m) of media expenditure on behalf of clients such as Burger King and Northwest Airlines. The agency was set up 10 years ago by former J Walter Thompson media director Richard Kostyra and has offices in New York and Minneapolis.
Media First will operate as an independent, standalone business unit within Interpublic's The Partnership division and report to Interpublic vice-chairman David Bell. Kostyra will continue in his role as president and CEO.
"We are pleased to be adding a specialised media company such as Richard's to our roster," Bell said. "A number of Interpublic agencies share important clients with Media First and have partnered successfully with them in providing integrated programmes to those clients."
Interpublic owns Initiative Media, the global media network, as well as advertising agencies such as McCann-Erickson WorldGroup and Foote, Cone & Belding.
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