Recently, Ir has attracted much attention for the use under high temperature environments, such as engine plug-tips, space planes, etc. This is because Ir has a high melting point, good chemical stability and mechanical stabilities at high temperatures. In addition, Hf addition to Ir is reported to enhance high temperature strength, and Ir-3at%Hf alloy exhibited over 80MPa of 0.2% compressive flow stress, compared with 19.4MPa of pure Ir at 2223K. On the other hand, Ir forms volatile oxides above 1173K, which could limit the long-term application under oxidative atmosphere. Further understanding of oxidation kinetics in the case of Ir alloys is thus important. Surface treatments on such materials should also be considered for oxidation protection. In our research group, aluminizing on Ir based alloys were successfully conducted to protect them against oxidation. This presentation describes the microstructure of aluminized Ir-based refractory alloys and their oxidation resistance.