Background: IMOD™, a selenium enriched extract of the plants Tanacetum vulgare, Urtica dioica, and Rosa canina, has an excellent effect on oxidative stress. In this study, we investigated the radioprotective effects of this immunomodulatory drug on human peripheral blood lymphocytes.Methods: Peripheral blood samples obtained from venipuncture of the brachial vein were treated with IMOD™ (5, 10, 15, 20 μl) for 30 min and Cobalt 60 γ-rays (0.25, 0.5, 1, 2 Gy) as the test groups and cultured with the control. We used the micronuclei assay, cell death detection, and cell toxicity assay to analyze the treatment effects.Results: The frequency of micronuclei were 1.66 (0 Gy), 5.33 (0.25 Gy), 9.67 (0.5 Gy), 17.67 (1 Gy), and 23.67 (2 Gy) in the irradiated lymphocytes (P<0.001). The percentage of micronuclei frequency reduced to 20%, 26.83%, 37.68%, 16%, and 20.47% with IMOD™. Apoptosis and necrosis decreased significantly in the IMOD™ treated groups (P<0.05).Conclusion: IMOD™ may protect these cells against ionizing radiation.