The grafting of ethyl methacrylate (EMA) onto guar gum (GG) was studied as a function of monomer and initiator concentration, time, pH, and temperature. The presence or dextrose improves the efficiency of ceric ion towards grafting. Acid hydrolysis and infrared spectroscopy were used for the confirmation of grafting. The degradability, thermal stability and physical properties of GG and a representative graft copolymer were evaluated. Based on reaction kinetics, a grafting mechanism has been suggested.