A thermal management system includes a first cooler that cools a first heat source, a first circulation path that connects the first cooler and a first pump, a second cooler that cools a second heat source, a second circulation path that connects the second cooler and a second pump, a changeover valve, and a controller. The changeover valve is switchable between first and second valve positions. The first and second circulation paths are separated from each other when the changeover valve is in the first valve position. The controller causes both the first and second pumps to operate when the temperature difference between refrigerants in the first and second circulation paths is more than a predetermined temperature difference threshold when the changeover valve is set to the first valve position and one of the first and second pumps is operating and the other is not operating.