In this work, aluminizing treatment to improve the oxidation resistance of two-phase [NiAl+Ni 3 Al] Ni aluminides was performed and their surface characteristics were compared with the same alloys without aluminizing treatment in terms of microstructure, oxidation behaviors at 1100 o C and hot corrosion resistance at 900 and 950 o C. Two-step treatment of high Al activity low temperature (HALT) aluminizing was performed to form a NiAl compound layer of approximately 230 μm thickness on the surface. Isothermal oxidation test at 1100 o C showed that at the early stage of oxidation up to 2 h a metastable θ-Al 2 O 3 phase was observed on the surface, which in turn would transform into dense equilibrium α-Al 2 O 3 phase in the later stage of oxidation. Due to these dense phase formed on the surface, much improved oxidation resistance in the aluminized two-phase Ni aluminide, especially in the Ni-32 at.%Al-0.5 at.%B alloy could be obtained. Also improved resistance against hot corrosion up to 950 o C was resulted from aluminized two-phase Ni aluminides.