The present study was carried out to investigate the antioxidant activity and the protective effects of the aqueous leaf extract of Moringa oleifera (MO) on α-radiation-induced toxicity in cardiac and pulmonary tissues in rats. Rats were administered MO (300mg/kg, oral gavage) for 15 consecutive days and 1h after the last dose, rats were exposed to 6Gy α-radiation. Irradiation toxicity was manifested biochemically by an increase in serum triglycerides, total cholesterol and low density lipoprotein-cholesterol, creatine phosphokinase and lactate dehydrogenase activities, elevation of MDA and NO(x) in examined tissues as well as a decrease in serum level of high density lipoprotein-cholesterol and tissue glutathione(GSH) level, catalase(CAT), glutathione peroxidase(GSHPx) and superoxide dismutase(SOD) activities. Marked DNA damage was observed. Pretreatment with MO showed a significant amelioration in the levels of lipid profiles, MDA, NO(x) and DNA damage. The antioxidant enzymes increased significantly along with the levels of GSH. The aqueous extract of MO exhibited strong scavenging effect on 2, 2-diphenyl-2-picryl hydrazyl (DPPH) free radical. Moreover, histopathological examination of heart and lung tissues confirmed the biochemical data. Our results show that pretreatment with MO extract minimize the oxidative stress of α-irradiation indicating its free radical scavenging and potent antioxidant activities.