Steel industry wastes (iron-containing waste) could be used as a Fenton-catalyst for the decolorization of methyl orange dye. Various reaction conditions were investigated including catalyst concentration, hydrogen peroxide concentration and pH value. The obtained results indicated that the dye degradation rate increases with increasing catalyst and hydrogen peroxide (H₂O₂) concentrations and with decreasing pH value. Over 98 % decolorization of the dye was achieved within 30 min at optimum reaction conditions; 200 mg/L catalyst and 34 mM H₂O₂ concentrations at pH 2 for 20 mg/L initial dye concentration. Reaction kinetics was also carried out to determine the order of reaction in both catalyst and H₂O₂ concentrations. Stability and reusability of Iron-containing waste were investigated. The iron-containing waste as catalyst can be reused several times with nearly same efficiency of Fenton-like oxidation of MO.