The extent of oxidation and mechanism involving glassy and nanocrystalline phases are found to be different than that in case of normal crystalline metals and alloys. A short review on oxidation behavior of metallic glass and nanocrystalline alloys is presented in the light of work by the present authors and other researchers. The main factors, which are important in controlling the oxidation of metallic glass, are: (i) structure of glass and its devitrified states, (ii) composition of the alloy, and (iii) structure of the oxide layer. Hence, these factors are discussed with the help of isothermal and non-isothermal oxidation both in air and in the presence of oxygen of a number of Zr-based glassy alloys. The oxidation resistance of the glassy alloys decreases in the following order: microcrystalline alloy > fully nanocrystalline alloy > partially nanocrystalline alloy > relaxed amorphous alloy > quenched amorphous Zr-based alloy. © 2015, The Indian Institute of Metals - IIM.