The oxidation behavior of an Fe₄₈Cr₁₅C₁₅Mo₁₄B₆Er₂ bulk metallic glass (Fe-BMG) was studied over the temperature range of 600–725°C in dry air. The oxidation kinetics of the glassy alloy followed a two-stage parabolic rate law at T≤650°C, while the single-stage linear rate was observed at higher temperatures (T≥675°C). The oxidation rates of the Fe-BMG at T≤625°C were much lower than those of the commercial 304 stainless steel (304 SS), revealing the excellent oxidation resistance of the amorphous alloy. A continuous, thin layer of chromium oxide (Cr₂O₃) containing some iron was formed at T≤650°C, while typical hump iron oxides intermixed with minor amounts of Cr₂O₃ and MoO₂ were observed at T≥675°C. In addition, a substrate phase transformation from the amorphous structure to Fe-Cr and FeCrMo crystalline phases was detected after the oxidation. Very likely, the formation of the non-protective Fe₃O₄ and MoO₂ breaks the scale integrity and allows the rapid cation/anion transportation, resulting in the fast linear-kinetics behavior of the Fe-BMG at T≥675°C.