A control system for a vehicular drive unit having an engine, a motor-generator for acting as a motor and a generator, a planetary gear including at least three rotary elements, a battery for storing electric power as generated by the motor-generator and for feeding electric power to drive the motor-generator, an engine controller for causing the engine to output a target output value on a best mileage curve; and a motor-generator controller for controlling the motor-generator. When the output of the motor-generator corresponding to a target output value of the engine is within an outputtable region of the motor-generator, the motor-generator controller causes the motor-generator to output a reaction torque corresponding to the output torque of the engine. When the output of the motor-generator is outside of the outputtable region, the motor-generator controller changes the target output value of the engine so that the output of the motor-generator is within the outputtable region, to thereby change the output of the motor-generator in accordance with the changed target output value of said engine.