The polysaccharide, kappa-carrageenan (kC), has been chemically modified by graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) in an aqueous medium using ceric ammonium nitrate (CAN) as an initiator under argon atmosphere. A plausible reaction mechanism of grafting has been suggested. Evidence of grafting was obtained by comparison of FTIR spectra of kC and homopolymer-free kC-g-poly(HEMA) as well as solubility characteristics and gravimetric analysis of the products. The optimum reaction conditions affording maximum grafting ratio and add-on value have been determined. The grafting parameters have been found to increase with increasing in kC, CAN, and HEMA concentrations as well as polymerization time and temperature, up to a certain value, but these parameters decrease on further increasing in reaction conditions.