He replaces Dana Anderson, who stepped down in August to spend time with her family.
This is the latest role in Carpenter's 18-year tenure at DDB. For the past five years, he headed the network's office in Los Angeles.
The appointment comes after a turbulent year for the DDB network, which saw the £250 million JC Penney account move to Saatchi & Saatchi last September.
Dick Rogers, the president of DDB North America, said Carpenter had "proven himself in the area of new-business development and consistently delivered key wins for the network".