A turbo machine including a heat exchanger flowpath is generally provided. The turbo machine includes an outer casing extended along an axial direction, a prediffuser defining an inlet passage into a combustion section of the turbo machine, an inner casing extended from the prediffuser, in which a diffuser cavity is defined between the outer casing and the inner casing, a first plenum wall extended outward along a radial direction from the prediffuser, and a second plenum wall extended outward along a radial direction from the prediffuser. The second plenum wall is separated along the axial direction from the first plenum wall. A plenum is defined between the first plenum wall and the second plenum wall. The turbo machine includes a heat exchanger including a first conduit in fluid communication with the diffuser cavity. The first conduit is in fluid communication with a passage, and a second conduit in fluid communication with the passage and the plenum. A flow of working fluid is admitted from the diffuser cavity through the heat exchanger to the plenum via the first conduit, the passage, and the second conduit.