A transmission fluid heater for a motor vehicle includes a fluid pan mounted on the transmission for storing a supply of transmission fluid. The fluid pan has an inner chamber storing the transmission fluid, and an outer chamber surrounding the inner chamber. An inlet to the outer chamber communicates with a source of engine exhaust gas and an outlet from the outer chamber exhausts the exhaust gas. An inlet valve opens and shuts the communication of engine exhaust gas to the inlet. A plurality of heat exchanger fins enhancing the transfer of heat from the engine exhaust gas within the outer chamber to the transmission fluid is stored within the inner chamber.