Background: DZN (diazinon) is an organophosphate insecticide that had been used in agriculture and for domestic and veterinary use for several years and caused many negative effects on plants and animal species, especially on human. The aim of present study was to evaluate the effects of DZN on MDA (malondialdehyde) and GSH (glutathione) levels in female rat reproductive tissue (ovary) and to assess the protective role of vitamin E. Methods: A total of 30 adult female Wistar rats were divided into five groups: control group (without any intervention), sham group (received only pure corn oil, as solvent), experimental group 1 (DZN+corn oil, 60 mg/kg), experimental group 2 (vitamin E, 200 mg/kg), and experimental group 3 (DZN+vitamin E, the same dosage). All drugs were injected intraperitoneally, except vitamin E which was administrated by gavage. The animals were scarified after two weeks and MDA as a marker of lipid peroxidation and GSH content were measured in ovarian tissue. Results: DZN reduced GSH content and increased MDA level in ovary compared with the control group (P<0.001). Vitamin E plus DZN increased GSH content but decreased DZNinduced MDA elevation in rat ovarian tissue. Conclusion: Oxidative stress contributes to DZN-induced ovarian toxicity. The results of this study suggested that vitamin E may have a protective effect on DZN-induced ovarian toxicity.