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The oxidation behavior of 22Cr25NiWCoCu stainless steel with 0−0.86 wt.% Nb addition was investigated at 900 °C in air. With an increase in Nb addition, the volume fraction and average particle size of Nb (C, N) increased, but the grain size decreased. The results of grazing incidence X-ray diffraction indicated that the steels with Nb additions promoted Cr₂O₃ formation. After 10−100 h of oxidation, Cr depletion occurred at the region with Nb (C, N) precipitates because of its high Cr consumption rate, leading to Fe oxide generation. Finally, after 100 h of oxidation, the outer layer of Fe₂O₃ and the inner layer of (Cr, Fe, Mn)₃O₄ were formed.