The effect of a carbon containing atmosphere on the microstructure and mechanical properties of Fe-32Mn-9.4Al-1C-1.27Si alloy was investigated in this work. Surface oxide nodules and grain boundary oxides were found to form on this alloy when it was annealed in carbon-containing air at 1050 degrees C for 1 h. The oxidation reaction was thought to be the result of the "green rot" attack process. This alloy was embrittled severely by the carbon-containing air through the formation of surface oxide nodules and grain boundary oxide. The carbon-containing air enhanced the oxidation rate of this alloy at 1050 degrees C. The structure of the oxide nodules formed on this alloy in the carbon-containing air was similar to that observed on a FeMnAl alloy heated in 1000 degrees C air for 24 h.