Poly(MA-alt-MVE)-g-PLA/ODA-MMT nanocomposite was prepared by self-catalytic interlamellar graft copolymerization of L-lactic acid (LA) onto poly(maleic anhydride-alt-methyl vinyl ether) copolymer in the presence of octadecyl amine-montmorillonite (ODA-MMT) organoclay. FTIR, H-1 (C-13) NMR, XRD, and SEM-TEM were utilized for characterizing the resultant nanocomposite. Lactase from Trametes versicolor was immobilized onto the prepared nanocomposite by adsorption or covalent coupling. Decolorization of Reactive Red 3 from aqueous solution by laccase immobilized on the nanocomposite was studied in different conditions (pH, temperature, dye concentration, and reaction time) to investigate the decolorization activity with repeated use and storage. The results indicated that more than 77% of the activity of laccase immobilized systems was retained at the end of 10 cycles. The final decolorization capacity of the immobilized laccase was significantly higher (65%) than that of free laccase (33%) in the chosen optimized conditions (pH 5, 20 degrees C, 0.05 mg/mL laccase concentration, and 90 min).