A vehicular heat pump system utilizing intermediate gas recompression is provided. The heat pump system is for use in a vehicle having a battery and a passenger compartment. The heat pump system may include a heating circuit and a cooling circuit each including a compressor having a first inlet and a second inlet and a vapor-liquid separator configured to separate intermediate pressure refrigerant supplied by a first expansion device into refrigerant in a gaseous state flowing therethrough and refrigerant in a liquid state flowing therethrough. The vapor-liquid separator may be configured to selectively inject refrigerant in a gaseous state into the compressor at the second inlet to increase the mass flow rate of the refrigerant. This allows the heat pump system to operate effectively in cold ambient temperatures. A method of operating a heat pump system utilizing intermediate gas recompression is also provided.