In a device for detecting the temperature of an oscillator crystal 2, arranged on a carrier, in particular in a mobile radio apparatus, the detected temperature should be as exact as possible a replica of the temperature to which the oscillator crystal 2 is subjected. For this purpose, a temperature sensor 7 is arranged on the carrier 1 in such a way that it is subjected to the same ambient temperature as the oscillator crystal 2 or the oscillator-crystal housing 2'. The temperature sensor 7 and the oscillator crystal 2 are located so as to be electrically parallel.