In this study, the biochemical and histopathological effects of thiamine and thiamine pyrophosphate on ischemia-reperfusion induced oxidative damage in rat ovarian tissue were investigated. Animals were divided into four groups of six rat each, ovarian ischemia-reperfusion (IR), 25 mg/kg thiamine + ovarian ischemia-reperfusion (TIR), 25 mg/kg thiamine pyrophosphate + ovarian ischemia-reperfusion (TPIR) and Sham group (SG). The results of the biochemical experiments have shown that the rat ovarian tissue with thiamine treatment, the level of MDA, GSH and the 8-hydroxyguanine are almost the same as the IR group; while in the group with thiamine pyrophosphate treatment, the level of MDA, GSH and the 8-hydroxyguanine are almost the same as the SG. Ovarian tissue of rats in the IR group were congested and dilated vessels, edema, hemorrhage, necrotic and apoptotic cells. In this group, the migration and the adhesion of the polymorphonuclear leucocytes to the endothelium were observed. Both ovaries in TPIR group, there was no difference according to the SG. Histopathology of ovarian tissues in the TIR group was almost the same with the IR group. Our results indicate that thiamine pyrophosphate significantly prevents the ischemia-reperfusion induced oxidative damage in ovarian tissue, whereas thiamine has no effect. In conclusion, we have found that thiamine pyrophosphate prevents oxidative damage due to ischemia-reperfusion injury, whereas thiamine does not have this effect. Furthermore, we have confirmed that the results of our biochemical analyses are in concordance with the histopathological findings.