Aflatoxin is among the natural toxins that cause serious side effects on living things. Diosmin is also one of the compounds with broad pharmacological effects. In this study, the effects on the oxidant/antioxidant system of 50 mg/kg body weight/day dose of diosmin, aflatoxin (500 mu g/kg body weight/day), and combined aflatoxin (500 mu g/kg body weight/day) plus diosmin (50 mg/kg body weight/day) given to the stomach via catheter female adult Wistar Albino rats is examined. Forty rats were used in the experiment, and these animals were randomly allocated to four equal groups. The test phase lasted 21 days, and blood samples and tissue (liver and kidney) samples were taken after this period was over. Some biochemical parameters (glucose, triglyceride, cholesterol, blood urea nitrogen, creatinine, uric acid, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total protein, albumin) and levels of malondialdehyde, nitric oxide, and 4-hydroxynonenal and activities of superoxide dismutase, catalase, and glutathione peroxidase were analyzed in the samples. The aflatoxin administered over the period indicated a significant increase in levels of malondialdehyde (MDA), nitric oxide (NO), and 4-hydroxynonenal (4-HNE) in all tissues and blood samples. Therewithal, the activity of antioxidant enzymes showed a change in the decreasing direction. Biochemical parameters of the group in which aflatoxin were administered alone changed unfavorably. Parallel effects were also observed in the histopathological findings of this group. The results showed that aflatoxin changed antioxidant/oxidant balance in favor of oxidant and eventually led to lipid peroxidation. Diosmin administration to aflatoxin-treated animals resulted in positive changes in antioxidant enzyme activities while the levels of MDA, NO, and 4-HNE were reduced in all tissues and blood samples examined. Diosmin alleviates the oxidative stress caused by aflatoxin. Similar improvement was observed in biochemical parameters of this group as well as in liver and kidney histopathology. No significant change was observed in the group treated with diosmin alone in terms of the parameters examined and histologic findings. As a result, diosmin may be included in compounds that can be used as a therapeutic and prophylactic agent in the event of the formation of aflatoxin exposure and poisoning in animals.