Ocimum africanum Lour. (hairy basil, hoary basil or lemon basil) is an aromatic herb in Asian and Thai cuisine that has been used as a carminative, a digestion enhancement and remedy for gastrointestinal disturbance in Thai traditional medicine. This study was performed to evaluate the gastroprotective effect of O.africanum leaf extract in acid/alcohol-induced gastric lesion in rats. Pretreatment of the plant extract can prevent the gastric damage in a dose-dependent manner. At 125 mg/kg of body weight, the plant extract attenuated the inflammation with % ulcer index of 5.08±1.41, whereas at doses of 250 and 500 mg/kg of body weight, the gastric lesion was completely prevented in the manner similar to what was observed in omeprazole pretreated animals (% ulcer index of 1.0±61.94, 0.1±10.45 and 0.00±0.00, respectively). The protective effect of the plant extract against acid/alcohol-induced gastric damage relates to its high antioxidative property and the ability to enhance the activities of three antioxidative enzymes, i.e. superoxide dismutase, catalase and glutathione peroxidase. Preliminary phytochemical investigation demonstrated that certain phenolic compounds such as rosmarinic acid, caffeic acid and vanillic acid might take part in the protective effects.