An actuator (12) for a device for clutch actuation in a motor vehicle has cylinder housing (14) with a pneumatic pressure connection (Ep) and at least one hydraulic pressure connection (EH1, EH2), in which cylinder housing a piston (16) is operatively connected to a longitudinally moveably control element (G). The piston together with the cylinder housing defines a pneumatic chamber (Kp) that can be pressurized via the pneumatic pressure connection. At least one hydraulic chamber (KH1, KH2) is connected to the hydraulic pressure connection. The chambers are separated from one another by a sealing arrangement (18, 20). In a very compact design of the actuator, a pneumatic operative surface (AH2) axially delimiting the hydraulic chamber are formed on the piston, so that by pressurizing the pneumatic chamber the control element can be longitudinally moved via the piston in an actuating direction (B) against an external return force acting in a return direction (R), and a piston movement can be controlled by a pressure build-up in the at least one hydraulic chamber.