A bicycle derailleur comprises a base member, a movable member, a motor unit, and a controller. The controller is configured to control the motor unit to rotate an output shaft of the motor unit at a first maximum voltage during a first shifting operation of the chain in a first shifting direction. The controller is configured to control the motor unit to rotate the output shaft of the motor unit at a second maximum voltage during a second shifting operation of the chain in a second shifting direction. The first maximum voltage is different from the second maximum voltage.