The dry running detection system for a pump includes an ultrasonic transducer (8) designed for arrangement inside a pump housing (24) and electrically connected to a frequency generator (2) producing an electrical signal having a predefined frequency. An analyzing unit (10) of the system analyses the electrical signal applied to the ultrasonic transducer (8) and is designed to detect whether the ultrasonic transducer (8) is in contact with a liquid or not on basis of the signal level of the electrical signal.