The cryogenic instrumentation of ProtoDUNE successfully operated during the first run of the experiment, providing a comprehensive monitoring of the cryostats, the cryogenics system and the detectors. It includes devices to measure the liquid argon level, the electron lifetime, the temperature of the liquid and gas argon, the pressure inside the cryostat and the contamination of the gas argon, as well as cameras to inspect the most critical detector elements. These systems and their performance are reviewed, and a few aspects of their future upgrade discussed.