Although there has been a substantial progress in conventional medical treatment and technology, the lack of improvement in the survival rate of cancer patients has led to studies examining novel modalities for improving the therapeutic efficacy of various treatments. Herbal medicines have been considered good prospects as alternative remedies on account of their long historical application, easy access and low cost. This study investigated the effect of a promising immunomodulator–ginsan, derived from a plant polysaccharide, on radioprotective activity by examining its ability to modulate the antioxidant system, reduce the level of DNA damage, stimulate hematopoiesis and regulate the cytokines.