Whitehead, the head of account management at JWT, will help oversee the day-to-day running of the agency, working closely with his fellow joint managing director, Joe Petyan. He will report to JWT's chief executive, Guy Hayward.
During his six years at the agency, Whitehead has led accounts at both a UK and global level, including Johnson & Johnson, Diageo and Nokia. Before joining JWT, he worked at Saatchi & Saatchi, spending time in the agency's UK and Asian offices.
Vick resigned from JWT last month, without a job to go to. He had worked at the agency since July 2008.
Following Whitehead's appointment, Sonali Fenner, a digital account director, has been promoted to the joint-head of account management. Fenner joined JWT in March from Grand Union.