Hamish McLennan (pictured), Y&R's chief executive, who picked Jaques to run the crucial North American region, cited "personal reasons" for the split. He will take on Jaques' responsibilities for the time being.
Jaques, 50, the former head of Y&R Asia, is expected to return to Hong Kong.
Jaques was the first major appointment made by McLennan when he took charge of the network which was plagued by account losses and high-level defections.
McLennan described Jaques' departure as "a challenge, not a setback".