A device for adjusting a dual-servo brake with internal shoes (9) being supported on a shoe-holder plate (2) so as perform floating selfreinforcing or automatic activation movements against a braking surface of a drum. The device comprises: adjustment elements (30) comprising thrust surfaces (31) cooperating with opposed counter-thrust surfaces (32) of a pyramidal end of an actuation elements (34) provided with a threaded portion (35) housed rotatably in a threaded through-hole (36) of a support element (37), the threaded through-hole being arranged substantially along an axis transverse the axis of the mutual separation or approach movement of the ends of the shoes, the support element further comprising support means (38) for housing the adjustement elements slidably so as to form, with the actuation element, a support ans thrust structure closed onto the opposed adjustment elements, the actuation element further comprising an operating extension which can be housed so as to float freely in a slot provided in the shoe-holder plate so that an activation end (41) projects from the brake.