Reactive oxygen species (ROS) and inflammation play important roles in the pathogenesis of ischemia/reperfusion (I/R) ovarian injury. The purpose of this in-vivo study is to evaluate the effect of osajin, a prenylated flavonoid with antioxidant and anti-inflammatory properties, on oxidative balance and ovarian damage induced by unilateral I/R. The study used 48 adult, female Wistar albino rats. In the controls (CN), only laparotomy was performed. In group CNOsajin, 200 mg/kg osajin was administered. In group IRVEHICLE, an ischemic period of 3 h was followed by reperfusion for 3 h; the bilateral ovaries were then removed. In groups IR Osajin100 and IR Osajin200 , after 3 h of ischemia, 100 and 200 mg/kg of osajin was given orally before reperfusion, respectively; after 3 h of reperfusion, the ovaries were removed. After the experiments, MPO, SOD and CAT enzyme activities and LPO levels was determined for the oxidative state and activities of PMNs. In addition, histopathological changes were examined in all rat ovarian tissues. Statistical analysis was performed using one-way ANOVA (with Duncan). According to biochemical and histopathological results, I/R increased LPO levels and MPO activities and infiltration of PMNs despite high-antioxidant SOD and CAT enzyme activity. Both dosage levels of osajin before I/R significantly decreased LPO level and MPO activity and PMN infiltration compared to those of the IR VEHICLE group, with the higher dosage causing greater decreases. In addition, results showed that treatment with osajin against ameliorated development of irreversible ovarian damage induced by I/R. These results suggest that osajin provides protections against ovarian I/R injury. Its mechanisms could be related to mitigation of oxidative stress and activities and to PMN infiltration.