The prophylactic effects of oleanolic acid (OA) isolated from chloroform extract (CE) of Flaveria trinervia against ethanol induced liver toxicity was investigated using rats. CE and OA at three different doses were tested by administering orally to the ethanol treated animals during the last week of the 7 weeks study. Silymarin was used as the standard reference. The substantially elevated serum enzymatic levels of serum glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, alkaline phosphatase and bilirubin in ethanol treated animals were restored towards normalcy by treatment of CE and OA. In vivo antioxidant and in vitro free radical scavenging activities were also positive for all the three concentrations of CE and OA. However, OA at 150 mg/kg showed significant activity when compared to the other two doses. Biochemical observations in support with histopathological examinations revealed that CE and OA possess hepatoprotective action against ethanol induced hepatotoxicity in rats.