A single-package air conditioning appliance includes a housing defining an outdoor portion and an indoor portion. An outdoor heat exchanger assembly is disposed in the outdoor portion. The outdoor heat exchanger assembly includes an outdoor heat exchanger and an outdoor fan. An indoor heat exchanger assembly is disposed in the indoor portion. The indoor heat exchanger assembly includes an indoor heat exchanger and an indoor fan. A compressor is in fluid communication with the outdoor heat exchanger and the indoor heat exchanger to circulate a refrigerant between the outdoor heat exchanger and the indoor heat exchanger. The single-package air conditioner unit also includes a make-up air module mounted on an external surface of the housing.