A control system for a variable displacement pump driven by a drive source for driving a vehicle is provided. The variable displacement pump pressurizes hydraulic oil, and is switchable between a full capacity operation in which a discharge flow rate is maximized and a partial capacity operation in which the discharge flow rate is lower than that in the full capacity operation. It is determined whether an operation for starting the drive source has been performed. A rotational speed of the drive source and a temperature of the hydraulic oil are detected. When the rotational speed of the drive source is equal to or higher than a predetermined rotational speed and the hydraulic oil temperature is equal to or lower than a predetermined temperature, immediately after the operation for starting the drive source is performed, the partial capacity operation of the variable displacement pump is performed. This control suppresses generation of untoward noises caused by the operation of the variable displacement pump when starting to drive the vehicle.