In this article, synthesis of graft copolymers of methyl methacrylate (MMA) onto Saccharum spontaneum L. fiber under the influence of microwave radiation (MWR) was carried out. Different reaction parameters such as time, initiator molar ratio, monomer concentrations, microwave power, pH, and solvent were optimized for maximum graft yield (62.3%). The graft copolymers thus formed were characterized by FT-IR, SEM, XRD, and TGA, DTA, and DTG techniques. Moreover, graft copolymers have been found to be more moisture resistant and also showed higher chemical and thermal resistance.