The present disclosure relates to an air conditioning system, particularly, to an air conditioning system comprising a supplementary heat source. The air conditioning system of the present invention may comprise: an outdoor unit, an indoor heat exchanger connected to the outdoor unit and including a temperature sensor, a supplementary heat source supplementarily installed for the outdoor unit and operating by means of an energy source different from that for the outdoor unit, a temperature control unit for controlling the temperature of an installation space into which cold air or warm air is supplied by the outdoor unit and the supplementary heat source, and a communication unit comprising an input unit connected to the temperature control unit, a first output unit connected to the supplementary heat source, a second output unit connected to the outdoor unit, and a control unit for processing signals among the input unit, the first output unit, and the second output unit.