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The oxidation behavior of Zr 2 [Al(Si)] 4 C 5 and Zr 3 [Al(Si)] 4 C 6 in air has been investigated. The oxidation kinetics of bulk Zr 2 [Al(Si)] 4 C 5 and Zr 3 [Al(Si)] 4 C 6 at 900-1300°C generally follow a parabolic law at a very short initial stage and then a linear law for a long period with the activation energy of 237.9 and 226.8 kJ/mol, respectively. The oxide scales have a duplex structure, consisting of mainly an outer porous layer of ZrO 2 , Al 2 O 3 , and aluminosilicate/mullite, and a thin inner compact layer of these oxides plus remaining carbon. The oxidation resistance of Zr 2 [Al(Si)] 4 C 5 and Zr 3 [Al(Si)] 4 C 6 has been improved compared with Zr 2 Al 3 C 4 , and is much better than ZrC due to larger fraction of protective oxidation products, Al 2 O 3 and aluminosilicate/mullite.