A device (1) for selection and engagement of the gears of a gearbox for a motor vehicle comprises a control shaft (10) mounted rotatable and axially movable with respect to the gear casing. Mounted on the control shaft is an engagement hub (16) having a radial engagement finger (17), for controlling the devices for engagement of the gears. The radial engagement finger (17) is configured to oscillate in the space comprised between two fingers (13, 14) of a selection mask (12), which is also mounted on the control shaft (10), is axially movable with the latter, and is guided with respect to the gear casing so as not to follow rotation of the control shaft (10) and of the engagement hub (16) when a gear is engaged. The means for guiding the selection mask (12) are, however, shaped in such a way that during the axial travel of the engagement finger (17) towards an extreme position preliminary to the engagement of the reverse gear, the selection mask (12) is forced to move temporarily into a rotated position, in which at least one of the fingers (13, 14) of the selection mask (12) actuates at least one of the selector devices of the forward gears. There is thus caused a stop of the rotation of the primary shaft of the gearbox, and consequently a subsequent silent engagement of the reverse is enabled.