Arsenic trioxide (As₂O₃) is an effective drug in the treatment of leukaemia and many solid tumours. In clinical trials, arsenic therapy is closely associated with hepatic toxicity. The present study was designed to investigate the efficacy of omega-3 fatty acid against As₂O₃-induced hepatotoxicity. A 4 mg/kg body weight (bw) of As₂O₃ was orally administered to Wistar male rats for 45 days. Hepatotoxicity was evaluated by biochemical tests, antioxidant assays and histopathological examinations. Arsenic accumulation was found in the liver tissue of rats treated with As₂O₃. Hepatoprotective efficacy of omega-3 fatty acid was analysed by the combination therapy with As₂O₃. In vivo studies revealed a significant rise in lipid peroxidation with concomitant decline in reduced glutathione, glutathione-dependant antioxidant enzymes and antiperoxidative enzymes in the liver tissue of rats treated with arsenic. The supplementation of omega-3 fatty acid at a dose of 50 mg/kg bw with As₂O₃ offers ameliorative effect against hepatocellular toxicity. Omega-3 fatty acid maintained hepatic marker enzymes, antioxidant enzymes and decreased lipid peroxidation. The combination treatment clearly reduced the hepatic structural abnormalities such as haemorrhage, necrosis and cholangiofibrosis in the rats treated with arsenic. This study concludes that the omega-3 fatty acid might be useful for the protection against As₂O₃-induced hepatotoxicity.