A device is described for mechanically coupling an actuator to a valve which is adjustable by a plunger that is displaceable along a z-axis. The device has (a) a retaining element which can be mounted on a connecting chassis of the actuator and which is embodied for engaging on two opposite sides of a connection piece of a valve body in a recess incorporated in the connection piece, and (b) a clamping device which is disposed on a section of the retaining element and which is embodied in such a way that when the clamping device is actuated the section of the retaining element is displaced parallel to the z-axis relative to the connecting chassis such that the connecting chassis bears against the connection piece. An actuator having a coupling device of said kind and a method for mechanically coupling an actuator to a valve are also described.