Hepatotoxicity is a condition of liver cell damage that is often caused by drugs such as isoniazid. Isoniazid (INH) is an anti-tuberculosis drug that, when used excessively can cause an increase in Reactive Oxygen Species (ROS) and trigger oxidative stress thereby inducing cell necrosis, especially in the liver. Cinnamon is a plant contains flavonoids, tannins, alkaloids, and essential oils that are useful as antioxidants and have the potential to have hepatoprotective effects. This study aims to determine the effect of ethanol extract of cinnamon (Cinnamomum burmanii) and its effective dose as hepatoprotection on aspartate transaminase (AST) levels in isoniazid-induced male rats. This study was a post-test only control group design laboratory experiment with sample of 25 male Wistar rats consisting of five groups: the normal control group was given aquabidest (K1), the positive control was induced with 200mg/kg isoniazid (K2), and three treatment groups were induced with 200mg/kg isoniazid and given cinnamon ethanol extract at a dose of 100, 200, and 400mg/kg for 14 days. At the end of the study AST levels were measured. Data were analyzed using the One-Way Anova test and Tukey's Post Hoc Test. The results showed that the ALT levels of the group given cinnamon at doses of 100, 200 and 400 mg/kg decreased significantly (p<0.05), that are 93,20 ± 8,55, 85,60 ± 8,23, and 71,20 ± 3,56 U/L, respectively. Cinnamon ethanol extract could prevent increases in isoniazid-induced AST in rats, thus having a hepatoprotective activity.