A device (1) for actuating a parking lock device (2) of an automatic transmission includes a piston (3) guided in a cylinder (5) and hydraulically displaceable counter to a spring force of an actuation spring (4). The piston (3) is form-lockingly fixable in a first position and in a second position by radially displaceable blocking elements (26) of a blocking device (15). The blocking elements (26) are radially displaceable by an actuation element (17). The radial displacement path of the blocking elements (26) and an operating condition of the actuation element (17) corresponding thereto in the first position of the piston (3) deviate from the radial displacement path of the blocking elements (26) and the operating condition of the actuation element (17) corresponding thereto in the second position of the piston (3).