A method for mounting and setting an actuator of an exhaust gas turbocharger and a suitable electric actuating device are provided. The actuating device has an axially movable actuating rod which is connected to a coupling element which for its part is connected via a pivot pin to an actuation section of a bypass valve, the actuation section being configured as a lever arm. In order to set the desired closed position of the bypass valve during a predefined actuation of the actuating device, the coupling element is first connected to the actuating rod while still being displaceable. Before the fixing, the position of the actuating device which corresponds to the closed position is set by application of the corresponding voltage to the electric actuating device. Subsequently, a prestressing force is applied to the coupling element coaxially with respect to the actuating rod via a pneumatic actuator.