Electric parking brake actuator for actuation of a parking brake in a motor vehicle, comprising a housing, a transmission mechanism which is accommodated in the housing and which is rotationally drivable by means of an electric motor, an actuating rod which is operatively connected with the transmission mechanism and which carries an actuating element for the parking brake, wherein the transmission mechanism serves the purpose of conversion of a rotational movement into an axial movement of the actuating rod so that the actuating rod is displaceable from an unblocking position to a blocking position and conversely, a spring element which biases the actuating rod in the direction of the blocking position, a blocking mechanism which serves the purpose of holding the actuating rod in the unblocking position of the actuating rod against the force of the spring element, and a locking device by means of which the blocking mechanism is releasable, wherein in a normal operation of the parking brake actuator the actuating rod is displaceable via the transmission mechanism driven by means of the electro motor, and wherein the blocking mechanism for an emergency operation of the parking brake actuator is selectably releasable by means of the locking device so that the actuating rod as a consequence of the force of the spring element moves into the blocking position without assistance by the electric motor, wherein the blocking mechanism comprises a blocking disc which is in drive connection with the transmission mechanism and which has a profile co-operating with the locking device, wherein in normal operation of the parking brake actuator the blocking disc can be driven by means of the electric motor in a first direction of rotation, characterized in that the profile of the blocking disc in the first direction of rotation allows rotation of the blocking disc independently of the locking device and the profile of the blocking disc in a second, opposite direction of rotation forms a stop surface which is able to be brought into contact with the locking device and which thus prevents rotation of the blocking disc in the second direction of rotation when the blocking disc adopts a rotational position in which the actuating rod is disposed in the unblocking position of the actuating rod, and wherein in emergency operation of the parking brake actuator the stop surface is releasable by the locking device so that the blocking disc rotates in the second direction of rotation, whilst the actuating rod under the force of the spring element moves into the blocking position. the blocking disc can be driven by means of the electric motor in a first direction of rotation, characterized in that the profile of the blocking disc in the first direction of rotation allows rotation of the blocking disc independently of the locking device and the profile of the blocking disc in a second, opposite direction of rotation forms a stop surface which is able to be brought into contact with the locking device and which thus prevents rotation of the blocking disc in the second direction of rotation when the blocking disc adopts a rotational position in which the actuating rod is disposed in the unblocking position of the actuating rod, and the stop surface is releasable by the locking device so that the blocking disc rotates in the second direction of rotation, whilst the actuating rod under the force of the spring element moves into the blocking position.