An oil supply system for a vehicle includes: a mechanical oil pump driven by an engine; an electric oil pump driven by an electric motor; a hydraulic pressure control circuit supplied with oil from the mechanical oil pump and the electric oil pump through an oil discharge passage for the mechanical oil pump and an oil discharge passage for the electric oil pump, which are connected to each other; a lubrication/cooling oil passage that is supplied with the oil from the hydraulic pressure control circuit; and a communication passage that provides communication between the lubrication/cooling oil passage and the mechanical oil pump. With this oil supply system, it is possible to prevent the electric oil pump from causing air-sucking noise, for example, in the motor-power cruise mode, and to improve the rising characteristics of the hydraulic pressure produced by the mechanical oil pump during startup of the engine.