Poly(acrylamide) has been efficiently grafted onto Cassia fistula seed gum using ceric ammonium sulphate/sodium disulphite redox system. The conditions for obtaining optimum % grafting (208 %) and % efficiency (92 %) are: acrylamide = 0.16 M, ceric ammonium sulphate = 0.026 M, sodium disulphite = 0.050 M, Cassia fistula seed gum = 25 mL (0.4 % (w/v)), and temperature = 40 ± 0.2 ºC. Cassia fistula-graft-poly(acrylamide) (CF-g-PAM) was characterized using FTIR and SEM studies. CF-g-PAM could very efficiently capture “Reactive Blue (RBH5G)” dye from its aqueous solution. The copolymer did not dissolve even under highly acidic pH conditions and was able to remove 99.4 % dye from 100 mg L -1 dye solution under the optimized conditions (pH= 2, rpm = 150, adsorbent dose = 30 mg, temperature = 40 ºC, and contact time = 4 h). The adsorption equilibrium data are better explained by Freundlich isotherm, which indicated the presence of heterogeneous adsorption surface sites at CF-g-PAM. Langmuir adsorption isotherm, indicated significantly high Qmax (500 mg g -1 ) for the adsorption. The dye adsorption followed a pseudo second order kinetics (k’ = 5.3 x 10 -3 g. mg -1 min -1 ), indicating chemisorption of the dye is taking place. The kinetic study also supported the intervention of some boundary layer control. The results revealed that ceric ammonium sulphate/and sodium disulphite redox system is an efficient system for grafting poly(acrylamide) onto Cassia fistula seed gum and CF-g-PAM behaved as an efficacious adsorbent for Reactive Blue H5G dye. In future, the material may be explored for the adsorption of other anionic azo dyes and may be developed as the proficient dye adsorbent.