A control system for a hybrid vehicle which comprises a drive system including an engine, a motor, a first clutch disposed between the engine and the motor, a second clutch disposed between the motor and a drive wheel, and a transmission disposed between the motor and the drive wheel, the control system comprising: a second clutch control means for disconnecting a torque transmission path between the motor and the drive wheel by the second clutch upon the engine start request; a motor rotational speed control means for reducing the motor rotational speed through a rotational speed control of the motor, when the torque transmission path between the motor and the drive wheel is disconnected; an engine start control means for engaging the first clutch to start the engine using the torque of the motor when the motor rotational speed is reduced and for fully engaging the second clutch after complete combustion of the engine; a shift control means, during a time from starting the engine to a time of full engagement of the second clutch with the torque transmission path between the motor and the drive wheel being disconnected, for concluding a downshift of the transmission, and a mechanical oil pump operable by a rotational drive power of the motor shaft of the motor, wherein the motor rotational speed control means is configured to set a target motor rotational speed for the motor rotational speed reduction to a value at which the discharge amount of the mechanical oil pump becomes a lower limit amount or more, characterized in that the motor rotational speed control means is configured to set a target motor rotational speed for reduction to a value at which the heat generation amount of the first clutch becomes the upper limit amount or less. a second clutch control means for disconnecting a torque transmission path between the motor and the drive wheel by the second clutch upon the engine start request; a motor rotational speed control means for reducing the motor rotational speed through a rotational speed control of the motor, when the torque transmission path between the motor and the drive wheel is disconnected; an engine start control means for engaging the first clutch to start the engine using the torque of the motor when the motor rotational speed is reduced and for fully engaging the second clutch after complete combustion of the engine; a shift control means, during a time from starting the engine to a time of full engagement of the second clutch with the torque transmission path between the motor and the drive wheel being disconnected, for concluding a downshift of the transmission, and a mechanical oil pump operable by a rotational drive power of the motor shaft of the motor, wherein the motor rotational speed control means is configured to set a target motor rotational speed for the motor rotational speed reduction to a value at which the discharge amount of the mechanical oil pump becomes a lower limit amount or more, characterized in that the motor rotational speed control means is configured to set a target motor rotational speed for reduction to a value at which the heat generation amount of the first clutch becomes the upper limit amount or less.