Naringenin, a phytoalexin found in grapefruits and tomatoes, has been reported to exhibit a wide range of pharmacological properties. In this study, we investigated the protective effect of naringenin on hepatic injury induced by dimethylnitrosamine (DMN) in rats. Oral administration of naringenin (20 and 50 mg/kg daily for 4 weeks) remarkably prevented the DMN-induced loss in body and liver weights and inhibited the elevation of serum alanine transaminase, aspartate transaminase, alkaline phosphatase, and bilirubin levels. Naringenin also restored serum albumin and total protein levels, and reduced the hepatic level of malondialdehyde. Furthermore, DMN-induced collagen accumulation, as estimated by histological analysis of liver tissue stained with Sirius red, was reduced in the naringenin-treated rats. A reduction in hepatic stellate cell activation, as assessed by alpha-smooth muscle actin staining, was associated with naringenin treatment. In conclusion, these results demonstrate that naringenin exhibited in vivo hepatoprotective and anti-fibrogenic effects against DMN-induced liver injury. It suggests that naringenin may be useful in preventing the development of hepatic fibrosis.