The present study was planned aiming to investigate the effects of atrazine herbicide exposure on stress biomarkers acetylcholinesterase activity (AchE) and cortisol, oxidative stress responses and the histopathological changes in liver of female Clarias gariepinus and the ameliorative effect of vitamin E supplementation (240mg/kg diet) on the degree of atrazine sublethal toxicity (1.37mg/l) for 6 weeks. Chronic exposure to atrazine revealed a marked inhibition in the activity of AchE. But, significant increase of serum cortisol level was recorded. Moreover, atrazine exposure was associated with a marked induction of oxidative damage in liver tissue as evidenced by increased level of lipid peroxidation (LPO) and reduced glutathione (GSH) content. Atrazine exposure also led to a significant increase in the activities of catalase (CAT) and superoxide dismutase (SOD).Furthermore, histopathological examination of the liver of exposed fish showed dilatation and congestion of blood vessels, fatty degeneration, necrosis and pyknotic nuclei of hepatocytes. However, fish fed diet supplemented with vitamin E exhibited protective effect by minimizing the atrazine-induced toxicity, through measured values more or less similar to the control group fish.