The present disclosure relates to a clamp-on ultrasonic sensor for an ultrasonic flow rate measuring device and to an ultrasonic flow rate measuring device comprising at least one clamp-on ultrasonic sensor according to the present disclosure. The clamp-on ultrasonic sensor is designed to generate at least one lamb wave mode in a measuring tube wall of a measuring tube of the ultrasonic flow rate measuring device. To ensure the use of the clamp-on ultrasonic sensor on different types of measuring tubes, the clamp-on ultrasonic sensor comprises a coupling element, which coupling element is adapted to a respective type of measuring tube.