Microstructures of oxidized Ti3AlC2 and Ti2AlC were investigated using transmission electron microscopy. The presence of Ti-rich precipitates in the Al2O3 oxide scale and the enrichment of Ti in the Al2O3 grain boundaries were identified. High diffusivity of Al in the carbides contributes to the selective oxidation of Al. Moreover, the adhesive strength between the oxide scales and the substrates exceeds 85 MPa. Strong adhesive strength contributes to the thermal-cyclic stability of the oxide scales.