The protective effects of quercetin against sodium fluoride induced oxidative stress were examined in rat’s liver. Rats were divided into five groups. The first group served as normal group that was treated with standard diet. The second group was intoxicated with sodium fluoride (600 ppm) through drinking water for 1 week. The third, fourth and fifth groups were treated with quercetin at a dose of 10 and 20 mg/kg and vitamin C (as the positive control) at a dose of 10 mg/kg intraperitoneally for 1 week before sodium fluoride intoxication, respectively. After 1 week, activities of superoxide dismutase and catalase, level of reduced glutathione and lipid peroxidation end product were determined in the homogenates of rat liver. The results of the present study suggested that quercetin protects rat liver from sodium fluoride induced oxidative stress, probably via its antioxidant activity.