The 29-year-old takes responsibility for 60 staff across offices in London, Paris and Farnham, Surrey.
Kelliher joined Whiteoaks five years ago from Capricorn Communications, where he was an account manager.
Co-founders Gill Craig and Bill Nichols have become joint chairs of the agency, whose annual fee income is around £2m.
Have you registered with us yet?
Register now to enjoy more articles and free email bulletins