He will take a significant equity stake in Admedia, where he will build relationships with major advertisers and their agencies.
Lace, 40, split with Lowe, where he was the chief executive, in May 2006 amid an internal investigation into his actions. Since then, he has been the chairman of the direct and digital agency Intelligent Marketing. Before Lowe, he was the chief executive of Grey, but left following the widespread distribution of a hoax e-mail that claimed he was planning a secret business venture.
Lace will look at growth potential in Admedia's existing business and complementary areas.
Philip Vecht, Admedia's joint chief executive, said: "Garry has an exceptional mix of corporate, agency, media and private-equity experience and contacts."