Electric CEO Laurence Percival will become director of creative and brand strategy and will sit on the group's marketing and media board. His 15-strong team will merge with Four's marketing and media unit.
Percival set up Electric in September 2002, following a stint as managing partner at AMD Advertising. He has also held senior creative positions with Grey, Publicis and Interfocus.
Following the acquisition, Four will have more than 140 staff across four offices.