The subject of the invention is an adapter (100) intended to connect a wiper to a drive arm (5) of a motor vehicle wiper system. The adapter (100) according to the invention comprises a head (1) and a body (2) which extend in the continuation of one another in a longitudinal direction of the adapter (100), and the adapter (100) according to the invention comprises a means (6, 61) of rotational connection to a connector (8) attached to the wiper (7). According to the invention, the adapter (100) is formed at least by an upper wall (10, 20) from which derive at least two lateral flanks (11, 21) so as to delimit an internal volume (101) in which the connector (8) is able to extend. The adapter (100) comprises a first immobilizing means (3) and a second immobilizing means (4), each configured to immobilize the adapter (100) on the drive arm (5) in a direction perpendicular to the upper wall (20). According to the invention, the first immobilizing means (3) is formed of at least one stud (33) which comprises a protrusion (32), and in that the second immobilizing means (4) is at least made up of a tooth (410) arranged at one end of a flexible tongue (40) and extending towards the body (2) of the said adapter (100).