Abstract: Silver nanoparticles were prepared from silver nitrate using Glycyrrhizic Acid (GLY), under sonication. The resultant golden yellow solution containing glycyrrhizic acid-silver nanoparticle complex (GLY-Ag) of particle size of less than 100 nm was analyzed for antioxidant activity by DPPH free radical scavenging activity and it was shown that GLY-Ag possesses higher free radical scavenging activity than GLY. Oral administration of GLY-Ag offered significant protection against gamma radiation induced cellular DNA damage as shown by the results of comet assay performed in bone marrow cells and blood leukocytes of mice exposed to various doses of whole body gamma radiation (0-6 Gy). GLY-Ag was also found to offer protection against the genotoxic effects of ionising radiation as shown by the results of micronucleus assay and chromosomal aberration analysis in whole body gamma irradiated mice (0-2 Gy). The complex offered significant protection to the hemopoeitic system from radiation injury (6 Gy) as shown by bone marrow cellularity, total blood count and endogenous spleen colony formation. Oral administration of GLY-Ag enhanced the survival of animals following a lethal dose of whole body gamma irradiation (8 Gy).