Abstract: An unreported photo-initiated graft copolymerization of acrylonitrile (AN) onto sodium salt of partially carboxymethylated psyllium (Na-PCMPSy, = 0.13) was studied using uranyl nitrate (UN) as a photo-initiator. The Optimal reaction conditions for affording maximum percentage of grafting were evaluated by successively varying various reaction parameters viz. concentrations of photo-initiator, nitric acid and monomer as well as reaction time, temperature and amount of substrate. At the optimum reaction conditions the maximum values of the grafting yields achieved were %G = 219.62 and %GE = 99.85. The influence of various reaction parameters on the grafting yields was studied. The reaction mechanism for photo-initiated synthesis of Na-PCMPSy-g-PAN was proposed. The photo-induced grafting copolymerization process was confirmed and the products were characterized by using FTIR, XRD and SEM techniques.