Objective: To evaluate the effect of various doses of Nigella sativa in isoniazid induced liver biochemical changes in Rabbits. Study design: Animal study Place of study: Department of Pharmacology and Therapeutics in collaboration of Animal house BMSI, JPMC Karachi. Method: In this animal study, 48 (N) healthy rabbits of either sex were randomly selected and equally divided in four groups (12 in each). Group I, was given only healthy diet. Group II, given Isoniazid at 50mg/kg body weight per day orally. Group III, was given Isoniazid 50mg plus Nigella sativa 500 mg/kg body weight/day orally and Group IV, given Isoniazid 50mg plus Nigella sativa 1gm/kg body weight/day orally. Treatment duration was 20 days. Liver biochemical changes i-e, Serum Total Bilirubin, ALT and AST were investigated on 00 and 21 days respectively. The data was collected on designed proforma and assessed statistically using SPSS version 16 and paired T- Test was applied. Results: In Group I the liver biochemical changes were non-significant on 00 and 21 days. (S. Total Bilirubin, p value = 0.06, ALT, p = 0.09 & AST, p = 0.74). Group II the parameters were significantly raised, when 00 and 21 days were compared. (S. Total Bilirubin p = 0.00, ALT p = 0.00 & AST p = 0.00). In Group III the liver biochemical changes noted both significant and non-significant when compared between 00 and 21 days. (S. Total Bilirubin p = 0.06, ALT p = 0.00 & AST p = 0.74). Group IV the liver biochemical changes were non-significant when compared between 00 and 21 days. (S. Total Bilirubin p = 0.06, ALT p = 0.09 & AST p = 0.74) Conclusion: Nigella sativa showed protective role on isoniazid induced liver toxicity in rabbits.