We evaluated the hepatoprotective and antioxidant effects of silymarin (SM) against carbon tetrachloride (CCl₄)-induced hepatocyte and liver injury in , 100, 300, and 600 g/mL silymarin were added to carp primary hepatocytes before (pre-treatment), after (post-treatment), or both before and after(pre- and post-treatment) incubation of the hepatocytes with 8 mmol/L CCl₄ in culture medium. We then measured lactate dehydrogenase (LDH), glutamate pyruvate transaminase (GPT), glutamate oxalate transaminase (GOT), superoxide dismutase (SOD), and malondialdehyde (MDA) levels. carp were fed a diet containing one of three concentrations of silymarin [0.1, 0.5, or 1 g/kg (diet)] for 60 d. Each fish was then given a single intraperitoneal injection of CCl₄ (30% in oil), and 72 h after the injection, we collected blood and liver samples from each fish. We measured the serum biochemical indices and liver tissue indices described above. Silymarin improved cell viability and decreased GPT, GOT, LDH, MDA, and SOD activity. Administration of silymarin at 0.5 and 1 g/kg diet for 60 d prior to CCl₄ intoxication significantly decreased GPT, GOT, in the serum, and increased SOD, glutathione peroxidase, catalase, glutathione, total antioxidant capacity, and MDA formation in liver tissue. However, these parameters, except for LDH, were not significantly altered in fish fed 0.1 g silymarin per kg diet. Our data suggest that silymarin -induced hepatotoxicity in fish, which is likely related to its antioxidant activity. We suggest that silymarin may be used as a hepatoprotective agent against fish liver diseases.