A device that controls a temperature of a battery onboard a motor vehicle includes an air-conditioning circuit of the motor vehicle in which circulates, as a first heat-transfer fluid, an air-conditioning fluid. The air-conditioning circuit includes at least one evaporator for direct transfer of heat emitted by the battery to the air-conditioning fluid and a compressor to increase a pressure and a temperature of the air-conditioning fluid. The device also includes a cooling circuit in which circulates, as a second heat-transfer fluid, a cooling fluid. The cooling circuit includes at least one first heat source to heat the cooling fluid and at least one main radiator to cool the cooling fluid that can be short-circuited. The cooling circuit also includes a battery radiator to directly transfer heat conveyed by the hot cooling fluid to the battery when the main radiator of the cooling circuit is short-circuited.