Chitosan-grafted-polyacrylamide (Chi-g-PAM) was tested as a potential depressant of pyrite in the bulk flotation of galena from a complex sulfide ore containing galena, chalcopyrite, sphalerite, and pyrite. Laboratory scale froth flotation tests were carried out in the presence/absence of Chi-g-PAM, sodium cyanide (industrially used pyrite depressant), chitosan, and polyacrylamide (PAM) at 50 g/t where sodium isopropyl xanthate was used as a collector. The following order of galena flotability (Gf) was observed: Gf /Chi-g-PAM > Gf /Chitosan > Gf /PAM > Gf /NaCN. Zeta potential measurements and adsorption density studies of polymer at mineral/liquid interface verified that Chi-g-PAM had a preferential adsorption onto pyrite as compared to galena. Results obtained from this work suggested that Chi-g-PAM could potentially be used to replace toxic inorganic depressants at the same time improving recovery and grade of galena (PbS) in the flotation concentrates.