Provided are an air conditioner and a method of controlling the same. The air conditioner includes an indoor unit including an indoor heat exchanger, a first outdoor unit connected to the indoor unit, the first outdoor unit including a first compressor compressing a refrigerant and a first outdoor heat exchanger, a second outdoor unit including an engine generating a power by using combustion gas, a generator supplying electricity into the first compressor by using the power generated in the engine, a second compressor compressing the refrigerant by using the power of the engine, and a second outdoor heat exchanger, and a controller determining an additional operation of the second compressor on the basis of required cooling or heating load while the first compressor operates.