An actuation device of an adjustment unit for automotive vehicle seats has a hand lever and a frame. The frame carries the hand lever and accommodates an output shaft. The hand lever adopts a central position when the actuation device is in a position of rest, and may be pivoted alternatively in the two directions of rotation against the action of an elastic means biasing it in the central position. The hand lever has a first driving region. An adjustment wheel having circumferential gear teeth is centred on the output shaft. A pivotal lever has a long hole surrounding the output shaft, has a left engagement region and a right engagement region substantially extending as a continuation of the long hole. These regions are both provided with teeth matching the gear teeth of the adjustment wheel and being disengaged from the teeth of the adjustment wheel in the position of rest of the actuation device. The pivotal lever is provided with a second driving region that is in engagement with the first driving region of the hand lever.