An electronic thermostat may include an internal housing including a partition defining a head chamber communicating with a cylinder head and a block chamber communicating with an engine block and the internal housing of which a head chamber hole and a block chamber hole are formed thereto, an external housing of which an outlet is formed thereto and the external housing covering the internal housing, a thermostat heater disposed to the partition, a first opening/closing portion including a first wax receiving heat from the thermostat heater and selectively closing or opening the head chamber hole and a second opening/closing portion including a second wax receiving heat from the thermostat heater and selectively closing or opening the block chamber hole.