Background and purpose: The wide spread use of pesticides in public health and agricultural programs has caused environmental pollution and increased risk of acute and chronic of human poisonings. Diazinon after malathion is one of the most commonly used OPCs in the world. Several studies suggest that organophosphate compounds that cause oxidative stress and lipid peroxidation.Materials and methods: The study was performed on the male Wistar rats. Animals were randomly divided into 15 groups and 4 weeks Chemicals (Diazinon, L-carnitine, and selenium) recived intraperitoneally. Group 1 (normal saline), 2 (soya oil), 3 (Diazinon 20 mg/kg), 4, 5 and 6 groups (doses 50, 100 and 150 mg/kg L-carnitine), 7, 8 and 9 groups (doses 50, 100 and 150 mg/kg L-carnitine+ Diazinon 20 mg/kg), group 10, 11 and 12 (doses 0.5, 1 mg/kg 2 sodium selenite), 13.14 and 15 groups (doses 0.5, 1 mg/kg 2 sodium selenite+Diazinon 20 mg/kg).24 hours after last injection, the animals received ketamine anesthesia and liver tissue was removed. After liver tissue homogenization, glutathione (GSH) level were determined by Elman method. Data was analyzed by SPSS software using one-way variance analysis and Tukey’s test.Results: Diazinon in compared with the control group decreased glutathione level and L-carnitine in a dose-dependent manner increases GSH levels. Selenium with 0.5 mg/kg dose resulted in a significant increase in GSH level compared with diazinon alone (P>0.05).Conclusion: Diazinon induced the production of free radicals and oxidative stress. The depleted GSH content is indicator of oxidative tissue injury. Selenium and L-Carnitine improved the body’s antioxidant status against organophosphate pesticide, such as diazinon.