Disclosed is a means to attenuate torsional vibration in a power unit transmission system generated by torque fluctuations in the engine in an automotive hybrid power unit, and thereby eliminate noise, such as chattering from the power transmission gears and muffled body noise, etc. Disclosed is a hybrid power unit control system for a hybrid power unit that is equipped with a first drive train, which is configured with a gear transmission mechanism linked to a first input shaft that transmits engine drive power via a first friction clutch; a second drive train, which is configured with a gear transmission mechanism linked to a second input shaft that transmits engine drive power via a second friction clutch; a motor generator, which is connected to said first input shaft or second input shaft; and a driven apparatus, which is driven by the drive power transmitted from the output shaft of the gear transmission mechanism of said first drive train or the output shaft of the gear transmission mechanism of said second drive train. Said motor generator is started as an electric power generator when fluctuation in the rotational speed of said engine, which is detected by a rotational speed sensor, exceeds a predetermined upper limit amplitude value, so that torque of opposite phase to said rotational speed fluctuation is applied to said engine with the same periodicity as said rotational speed fluctuation.