An integrated heat exchanger and muffler unit (50,120,140) is provided for transferring heat between a first fluid and a second fluid, and for muffling the noise of the first fluid. The unit includes a housing (52) including a first inlet (60) for the first fluid, a first outlet (62) for the first fluid, a second inlet (64) for the second fluid, and a second outlet (66) for the second fluid. The unit (50,120,140) further includes a resonator (76) in the housing (52) and connected between the first inlet and outlet (60,62) to muffle noise in the first fluid, and a heat exchanger core (11,122) in the housing (52) connected to the first and second inlets and outlets to transfer heat between the first and second fluids. In one embodiment, the heat exchanger core surrounds the resonator. In another embodiment, the resonator surrounds the heat exchanger core.