The present study was conducted to study the ameliorating effect of Nigella sativa seed oil (5ml/ kg body weight, 10 ml/kg body weight) on the liver damage caused by thioacetamide (20 mg/kg body weight) in albino rats for a period of eight week. A significant (p<0.05) improvement in the altered levels of bilirubin, albumin, total protein, alanine transaminase, alkaline phosphatase, γ-glutamyl transferase was observed after treatment with 10 ml/kg body weight of Nigella sativa oil. Antioxidant enzymes like catalase, superoxide dismutase glutathione peroxidase, thiobarbituric acid reactive substances and reduced glutathione also showed significant improvement in their altered levels in Nigella sativa (10 ml/kg body weight) treated rats. The results confirm the ameliorating effect of Nigella sativa oil on liver injury caused by thioacetamide and suggest the ability of Nigella sativa oil in scavenging the free radicals and protecting the liver cell against oxidative damage. The histopathological examination of liver section also confirm the ability of Nigella sativa oil in decreasing the severity of histopathological injury caused by thioacetamide.