The disclosure relates to a derailleur assembly including a base member, a movable member, a driving module and a power module he driving module includes a casing and a motor, wherein the casing is pivotably disposed on the base member via a first pivot shaft, the casing is pivotably disposed on the movable member via a second pivot shaft, and the motor is disposed in the casing. The power module includes a base body and a battery assembly, wherein the base body is pivotably disposed on the base member via a third pivot shaft, the base body is pivotably disposed on the movable member via a fourth pivot shaft, and the battery assembly is disposed on the base body and is electrically connected to the motor.