The isothermal oxidation resistance of Al2O3–TiC composites with 3wt.% and 5wt.% cobalt is investigated at 800–1000°C in air for 25h. The oxidation resistance of Al2O3–TiC composites with 5wt.% cobalt is better than that of ones with 3wt.% cobalt. The general rate constant k and oxidation exponent n depend on the cobalt content and oxidation temperature. The oxidation kinetics of Al2O3–TiC composites with 3wt.% and 5wt.% cobalt both followed a rate that is slightly faster than the parabolic-rate law at 800–1000°C. The activation energy of the Al2O3–TiC composites with 5wt.% cobalt is larger than that of ones with 3wt.% cobalt at 800–1000°C.