A bicycle electric/electronic derailleur has a plurality of mutually movable components: a support body configured to be attached to a bicycle frame, a chain guide, and a pair of connecting arms, for connection between the support body and the chain guide at respective geometric articulation axes. A geared motor controls the motion of the plurality of mutually movable components. At least one first component has a case with a chamber containing the geared motor and/or one or more electric/electronic devices. The chamber crosses at least one articulation axis. The case comprises a blind hole that is coaxial with the one axis and open outwards of the case. A second component has a pivot pivotable in the blind hole.