A heat pump defrost system for efficiently defrosting an outdoor coil while simultaneously operating the heat pump in a normal heating manner. The heat pump defrost system generally includes a primary flow circuit including an indoor heat exchanger, an outdoor heat exchanger, a compressor connected thereto and a reverse valve for toggling a direction of refrigerant flow therethrough, and an auxiliary flow circuit for deicing the outdoor heat exchanger. The auxiliary flow circuit includes a valve for connecting the auxiliary flow circuit to the primary flow circuit, a heat sink in line with the auxiliary flow circuit, wherein the heat sink stores defrost fluid within the auxiliary flow circuit, at least one thermostat to read an outdoor ambient temperature and a control unit for operatively engaging the valve to direct the hot gas from the compressor of the primary circuit within the auxiliary flow circuit and the heat pump according to the outdoor ambient temperature for deicing the outdoor heat exchanger.