BACKGROUND Acetaminophen (APAP) as an analgesic and antipyretic drug can result to liver damages while using more than 4 g/day. Therefore, APAP toxicity causes the liver to dysfunction. This study aims to investigate the hepatoprotective and antioxidant activity of hydroalcoholic extract of watercress (WC) in APAP-induced hepatotoxicity in rats. METHODS Randomly, twenty-four Wistar rats were divided into four groups of six each. Groups named as control, APAP, APAP + WC and APAP + S for group 1, 2, 3, and 4, respectively. Group 1 received distilled water 1 ml/kg for 7 days. In group 2, 3, and 4, rats pretreated by receiving distilled water (1 ml/kg), WC extract (500 mg/kg), silymarin extract (mg/kg) for 7 days, respectively. Of note, to induce acute hepatotoxicity in groups 2, 3, and 4, rats posttreated by orally intoxicated with single dose of APAP (2 g/kg) on the sixth day. The animals were sacrificed on the seventh day. Alanine amino transferase (ALT), aspartate amino transferase (AST), ferric reducing ability of plasma (FRAP), protein carbonyl (PCO), total thiol (T-SH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) activities were measured in plasma. It should be noted that the chemical composition of WC extract was identified by GC-MS analysis. RESULTS The results have shown that there was a significant increase in AST, ALT, FRAP and PCO content in APAP group in comparison to control. Also, there was a significant reduction in T-SH levels and GPx activity in APAP group compared to control. However, administration of WC extract and silymarin not only causes a significant decrease in AST activity, but they markedly increased T-SH content and GPx activity compared to APAP group. GC-MS analysis showed the major compositions were found to be benzenepropanenitrile (48.30 %), Phytol (10.10 %), α-cadinene (9.50%) and linolenic acid (8.0). CONCLUSIONS It is concluded that the WC extract reduces APAP-induced toxicity through its hepatoprotective and antioxidant activity in rats.