An electric derailleur motor unit is provided for a motorized derailleur assembly. The electric derailleur motor unit has a derailleur motor support, a derailleur motor and an output shaft. The derailleur motor is mounted to the derailleur motor support. The output shaft is operatively coupled to the derailleur motor and rotatably supported on the derailleur motor support. The output shaft has an eccentric drive pin that is offset from a rotational axis of the output shaft. A drive train is provided between the derailleur motor and the output shaft. The drive train has at least one intermediate gear operatively coupled to the driving shaft of the derailleur motor and a worm gear operatively coupled to the intermediate gear such that rotation of the driving shaft of the derailleur motor rotates the intermediate gear which in turn rotates the worm gear.