Background: Ethanol causes hepatic cellular damage by alterations in biological functions. This study evaluated the hepatoprotective potential of the methanolic extract originating from Firmiana simplex (Sterculiaceae) stem bark against the ethanol-induced hepatotoxicity in rat primary hepatocytes. Materials and Methods: The extract of F. simplex stem bark was successively fractionated into n-hexane, chloroform, ethyl acetate (EtOAc), and n-butanol. Column chromatography with silica gel and sephadex LH-20 was used to isolate the EtOAc fraction. Rat primary hepatocytes were cultured to study the hepatoprotective activity of isolated substances against ethanol-induced toxicity. Intracellular reactive oxygen species (ROS) levels, the antioxidant activities of glutathione reductase (GR) and glutathione peroxidase (GSH-P X ) enzymes, and the GSH content were measured to examine the antioxidative property of the isolated compounds. Results: Two flavonoid glycosides, quercitrin (1) and tamarixetin 3-O-rhamnopyranoside (2), were isolated from the active EtOAc fraction. Compound 1 significantly protected rat primary hepatocytes against ethanol-induced oxidative stress by reducing the intracellular ROS level and preserving antioxidative defense systems such as GR, GSH-P X , and total GSH. Conclusion: This is the first report on the hepatoprotective activities of the extract of F. simplex. The EtOAc fraction of F. simplex stem bark and its major constituent quercitrin (1) could function as hepatoprotective agents to attenuate the development of alcoholic liver disease.