This study was carried out to determine the chemoprotective potential of a polyherbal aqueous decoction comprised of Nigella sativa (seeds), Hemidesmus indicus (roots), and Smilax glabra (rhizome) against bleomycin induced cytogenetic damage in human lymphocytes. Isolated peripheral blood lymphocytes (PBLs) were exposed to bleomycin at a dose of 40 µg/mL for 2 hrs in the presence or absence of different doses of the decoction (100, 300, and 600 µg/mL). Modulatory effect of the decoction on bleomycin induced cytogenetic damage was evaluated by (a) degree of chromosomal aberrations (CA), (b) formation of micronuclei (MN), and (c) induction of γH2AX foci in lymphocytes exposed to bleomycin. Lymphocytes pretreated with the decoction showed that a significant reduction (p < 0.05) in bleomycin induced (a) stable and unstable chromosome aberrations (CA), (b) MN formation, and (c) formation of γH2AX foci, when compared to lymphocytes treated only with bleomycin. The decoction by itself did not induce any significant cytogenetic damage in PBLs. Overall results of the present study confirm that the decoction can attenuate the cytogenetic damage mediated by bleomycin in human PBLs.