In this article, morphological modification of Sacccharum spontaneum L, a natural fiber through graft copolymerization with methylmethacrylate using ferrous ammonium sulfate-potassium per sulfate redox initiator has been reported. Different reaction parameters Such as reaction temperature, time, initiator molar ratio, monomer concentration, pH and solvent were optimized to get maximum graft yield (144%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron rnicroscopy, X-ray diffraction and thermogravimetric, differential thermal analysis, and differential thermogravimetric techniques. Graft copolymer has been found to be more moisture resistant and also showed higher chemical and thermal resistance. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113:1781-1791, 2009