Jowett's job title and start date are yet to be finalised, but his appointment is a precursor to wider changes at Aegis Media. He will report to Martyn Rattle, the chief client officer at Aegis Media.
Jowett became the managing director of MediaCom UK in March 2009, replacing Jane Ratcliffe, who was made the UK chief executive in 2008.
Before this, Jowett was the agency's commercial director. He joined MediaCom in 2000 as its deputy broadcast director from the Publicis agency MediaVest.
Earlier this month, Campaign revealed that Rob Horler, the managing director of the Aegis agency Carat, was to move to the role of chief operating officer of Aegis Media UK. Carat's deputy managing director, Steve Hobbs, will become the director of media operations at Aegis Media.
Aegis Media was unavailable for comment as Campaign went to press.