Abstract: Background and Objective: Isoniazid (INH) still represents a first-line drug for the treatment and prophylaxis of tuberculosis but different adverse reactions frequently develop in patients administered this drug. Rutin is a common dietary flavonoid consumed in fruits, vegetables and plant-derived beverages. Rutin showed in different reports anti-inflammatory and antioxidative properties. The aim of this study was to evaluate the antioxidative activity of rutin against the INH-induced hepatic toxicity using certain physiological criteria corroborated with a histopathological study of the liver. Materials and Methods: Eighty male albino rats were randomly divided into 4 groups: Control, INH-treated, (rutin+INH)-treated and rutin-treated groups. The INH and rutin were orally administered at dose levels of 54 and 40 mg kg–1 b.wt., respectively, daily for 4 weeks. Liver function markers were determined in serum in addition to the hepatic malondialdehyde (MDA) and glutathione (GSH) concentrations and superoxide dismutase (SOD) activity. These were supported with a histopathological study of the liver. Statistical analysis was carried out using t-test and analysis of variance (ANOVA). Results: Serum albumin concentration was reduced in INH-treated rats while the level of serum globulin was increased. So, serum albumin/globulin(A/G) ratio was significantly reduced (p<0.05). The activities of serum aspartate and alanine aminotransferases (ASAT and ALAT) and alkaline phosphatase (ALP) were significantly elevated(p<0.05) in association with INH administration being indicative to the liver affection. The endogenous antioxidant system showed a decrease in the hepatic GSH content and SOD activity concurrent with elevated liver MDA concentration. The administration of rutin 1 h prior to the INH treatment resulted in the amelioration of these alterations suggesting a hepatoprotective role of rutin. The administration of rutin alone did not alter the studied parameters. The histopathological part supported the biochemical study by ensuring alteration of liver structure and infiltration of leukocytes to the hepatic tissue in INH-treated rats and the amelioration of these alterations because of the pretreatment with rutin. Conclusion: This study revealed that INH at a high therapeutic dose level could induce a hepatic injury but the co-administration of rutin could ameliorate this effect via its antioxidative activity.