There is shown a hydraulic control system for a transmission of the type wherein a gearing mechanism is combined with a V-belt type continuously variable transmission mechanism. The system comprises a hydraulic arrangement wherein a hydraulic fluid pressure supplied to a pulley cylinder chamber which the tension of the V-belt is variable with. The level of the hydraulic fluid pressure is elevated or increased immediately before or during shifting from the torque transmission through the gearing mechanism to the torque transmission through the V-belt type continuously variable transmission mechanism.