The aim of this study was to evaluate the protective effects of vitamin E and/or curcumin against diazinon (DZN) (an organophosphorus insecticide)-induced toxicity of blood, liver and erythrocyte markers of male Wistar rats. The exposure of rats to DZN for 21 days provoked significant changes in red blood cell counts and hemoglobin. Results showed that lipid peroxidation increased significantly in DZN-treated rats, as evidenced by high liver and erythrocyte thiobarbituric acid reactive substance levels. Alteration of the antioxidant system in DZN-treated rats was confirmed by the significant decrease in the activity of catalase, glutathione peroxidase and glutathione-S-transferase, accompanied by a decline in reduced glutathione content in both tissues. On the other hand, a significant increase in the activities of plasma aspartate transaminase, alanine transaminase, lactate dehydrogenase and alkaline phosphatase was observed in the rats treated with DZN. However, the administration of vitamin E and curcumin has ameliorated the previous markers. In conclusion, our results indicate that the natural antioxidants like vitamin E and curcumin can effectively lower the erythrocytes and hepatic injuries induced by DZN as monitored by lipid peroxides, antioxidant enzyme activities and sensitive serum enzyme levels.