The present study was undertaken to evaluate the effect of diallylsulphide (DAS) against mercuric chloride (HgCl2)-induced oxidative stress in rat livers. Rats were randomly divided into four groups of six rats each and exposed to HgCl2 (50 mg/kg/body weight (b.w.)) intraperitoneally and/or DAS (200 mg/kg/b.w.) by gavage. HgCl2 administration enhanced alanine aminotransferase (AST) and aspartate aminotransferase (ALT) levels (p < 0.05) with reduction in the levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). However, treatment with DAS markedly attenuated HgCl2-induced biochemical alterations in liver and serum transaminases (AST and ALT; p < 0.05). Further, biochemical results were confirmed by histopathological changes as compared to HgCl2-intoxicated rats. Histopathology of liver also showed that administration of DAS significantly reduced the damage generated by HgCl2 The present study suggests that DAS shows antioxidant activity and plays a protective role against mercury-induced oxidative damage in the rat livers.