A motor vehicle rear spoiler includes: an elongate external wall having a front edge and an opposite rear edge, and an internal housing; two substantially parallel longitudinal mounting brackets situated inside the internal housing; and a signal receiving device including a receiving plate having two opposite borders and a receiving casing installed on the plate between the opposite borders. The two opposite borders are designed to be secured respectively to the two mounting brackets. The longitudinal mounting brackets each include a slideway for respectively receiving the opposite borders of the receiving plate in a sliding manner.