A bicycle battery holder is basically provided with a battery holder body, an operating member and a battery engaging member. The battery holder body includes a contact portion. The operating member is movably mounted to the battery holder body between a first position and a second position. The battery engaging member is pivotally coupled to the operating member on an axle such that the battery engaging member moves in a first direction with respect to the battery holder body to a battery retaining position as the operating member moves from the first position to the second position. The contact portion of the battery holder body limits rotational movement of the operating member around an axis of the axle to maintain the operating member in the first position while the operating member is disposed in the first position.