Hepatoprotective activity of Foeniculum vulgare (fennel) essential oil was studied using a carbon tetrachloride-induced liver fibrosis model in rats. The hepatotoxicity produced by chronic carbon tetrachloride administration was found to be inhibited by Foeniculum vulgare essential oil with evidence of decreased levels of serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and bilirubin. Histopathological findings also suggest that Foeniculum vulgare essential oil prevents the development of chronic liver damage. The changes in body weights in the rats assigned to the study groups supported these biochemical and histopathological findings. The results of this study clearly indicate that Foeniculum vulgare essential oil has a potent hepatoprotective action against carbon tetrachloride-induced liver fibrosis in rats.