A control system for hybrid vehicles to eliminate the shortage of drive force within the low-to-mid speed range in the hybrid mode. In a differential mechanism, a first rotary element is connected to an engine, a second rotary element is connected to a first motor, a third rotary element is connected to a second motor, and a fourth rotary element is connected to an output unit. A third motor is connected to the output unit. When the controller determines that the hybrid vehicle is propelled by the torque of the engine, the first motor and the second motor generate torques in a same direction as an engine torque to propel the vehicle in a forward direction, and the third motor generates a torque in the forward direction to propel the vehicle together with the engine torque.