Abstract Thymoquinone (TQ) has shown hepatoprotective effects in various experimental studies. We aimed to investigate the possible beneficial effects of TQ regarding its prevention of alpha-amanitin induced hepatotoxicity in human C3A hepatocytes. After administering alpha-amanitin in a concentrations of 1 and 10µg/mL on the cells in a hepatocyte cell line, TQ was administered in various concentrations (10, 5, 1, 0.5, 0.1, 0.05, 0.01, 0.005 µg/mL). The MTT test was used to determine cell viability. For the groups given only TQ at various concentrations, the cell viability rates at 48 hours post-administration were found at 82.6, 98.3, 102.1, 102.5, 99.4, 99.4, 101.9 and 106.3%, respectively. For the group with 1μg/mL alpha-amanitin and various TQ concentrations, the cell viability rates were found at 74.6, 88.5, 87.4, 88.7, 85.7, 86.8, 88.4, and 92.9%, respectively. For the group with 10μg/mL alpha-amanitin and various TQ concentrations, the cell viability rates for each TQ subgroup were found at 65.2, 79.2, 81.4, 81.1, 81.8, 81.8, 82.2 and 91.9%, respectively. Our study is the first in vitro study that investigates TQ’s effects on alpha-amanitin induced hepatotoxicity. Although TQ had beneficial effect in low doses did not significantly increase cell viability in liver damage due to alpha-amanitin toxicity.