He will serve as managing director of Momentum, New York, reporting to Momentum Global Chairman-CEO Chris Weil.
Mr. Grogan most recently served a five-year stint as president of Berlin Cameron, the shop he exited in May.
At the time, he told Adage.com he expected to leave the ad business for good, despite a 27-year agency career managing blue-chip accounts at Madison Avenue heavyweights such as Omnicom Group's BBDO Worldwide and McCann Erickson. Mr. Grogan's wife, Lori Senecal, serves as president of the latter's New York office.
"I knew I needed to do something else and be somewhere else," said Mr. Grogan. "I was not looking for a traditional advertising play."
"I looked at a range of options across the industry, outside of the industry, and at the end of the day, came back home. I talked to various holding companies ... but for me, there was a history and a familiarity with the organization to talk candidly about what I was looking for."
Mr. Grogan will help helm the New York office of Momentum, which has a presence in more than 50 countries. Key clients include American Express, Verizon, Coca-Cola, Kraft, Anheuser-Busch and Microsoft.