Executive partner Joe Petyan will take the role of regional director, Europe.
Both Whitehead and Petyan will report to JWT’s European chief executive, Toby Hoare.
Russell Ramsey, the third executive partner, remains executive creative director and reports to worldwide chief creative officer Matt Eastwood.
Whitehead and Petyan have led the London agency for seven years, having been appointed as joint managing directors in 2009. Along with Ramsey, they were promoted to executive partners in 2012 following the departure of Guy Hayward.
As chief executive, Whitehead will have full responsibility for the agency, its clients and its integration with specialist divisions such as digital innovation and ecommerce arm Mirum, content shop Colloquial and shopper marketing unit Geometry@JWT.
Petyan takes on operational responsibility for markets across Europe but will continue in his role as WPP team lead for HSBC globally.
Ramsey joined JWT in 2007 from Bartle Bogle Hegarty.