NiAl nanoparticles were synthesized by hydrogen plasma-metal reaction method. In order to study the oxidation behavior of the intermetallic nanoparticles, the changes in morphology, particle size and crystal structure during heat treatment in air were investigated by TEM, XRD and TGA. The NiAl nanoparticles were stable in shape at 1073 K in air, the oxide film formed around the nanoparticles during heating in air was contributed to prevent the nonparticles growth and further oxidized. The oxidation of NiAl nanoparticles proceeded slowly below 973 K and rapidly above this temperature. The NiAl nanoparticles were oxidized as Al2O3 preferentially, and then NiO formed. (c) 2007 Elsevier B.V. All rights reserved.