An in-vehicle temperature control system includes a refrigeration circuit including an inter-media heat exchanger that dissipates heat from a refrigerant to a heat medium, the refrigeration circuit being configured to realize a refrigeration cycle, and a heat circuit including a heater core, the inter-media heat exchanger, and an engine heat circuit. The heat circuit includes an adjusting valve. When heating is performed by using heat obtained by the refrigeration cycle, the adjusting valve is controlled to a first state where the heat medium flows into the heater core from the inter-media heat exchanger, and when heating is performed by using heat obtained by an internal combustion engine, the adjusting valve is controlled to a second state where the heat medium flows into the heater core from the engine heat circuit.