This study investigated the high temperature oxidation of Ni–Fe–Cr–Al porous metal. Two types of open porous metals with pore sizes of 30 and 40 PPI were used. For 24-h, the isothermal oxidation TGA tests were conducted at three different temperatures of 900, 1000, and 1100 °C. The oxidation resistance of porous metal decreased with decreasing pore size. Porous metals mainly created oxides such as Al2O3, Cr2O3, NiAl2O4, and NiCr2O4. The porous metal represented increasingly faster dwindling of Al and Cr content and easy progress to internal oxidation, comparing to the oxidation of bulk metal.