A thermowell system for measuring a process temperature includes an elongate thermowell having a proximal end and a distal end configured to extend into a process fluid. An infrared sensor is configured to detect infrared radiation from the distal end of the thermowell and responsively provide a sensor output. Vibration detector circuitry is coupled to the infrared detector and configured to detect vibration of the thermowell as a function of oscillations in the sensor output.