An electrical accessory (1) for installing in a wall, includes: a support portion that is adapted to be fastened to the wall and that includes at least one electrical box (80); an electrical unit (50) including at least one base (51) that houses an electrical mechanism (52) and that is provided with at least one snap-fastener tab (60) that is adapted to be snap-fastened on the support portion; and a front portion (10, 30) including a front wall (11) and at least one tongue (20) that extends at the rear of the front wall so as to fasten to the electrical unit. The tongue is adapted to be interposed between the snap-fastener tab and a rigid portion of the base of the electrical unit.