A thermal management system (1) includes a five-way valve (180) configured to switch a first circuit mode in which a chiller (142) and a battery (163) are thermally connected and a second circuit mode in which the chiller (142) and an LT radiator (122) are thermally connected, and an ECU (500) configured to control a compressor (151) based on a chiller temperature and a radiator temperature. The ECU (500) is configured to, in a case where switching between the first circuit mode and the second circuit mode is performed by controlling the five-way valve (180) during a heating operation of a refrigeration cycle (150), control the compressor (151) to reduce a temperature difference between the chiller temperature and the radiator temperature prior to the switching.