The antiulcerogenic effect of a hydroethanolic extract of Anacardium occidentale L. leaves was investigated. The extract inhibited gastric lesions induced by HCl/ethanol in female rats. A dose-response effect study showed that the ED50 was 150 mg/kgb.w. Extract doses higher than 100 mg/kgb.w. were more effective than 30 mg/kg of lansoprazol in inhibiting gastric lesions. A methanolic fraction (257.12 mg/kg) which reduced gastric lesion at 88.20% is likely to contain the active principle of the antiulcer effect. No signs of acute toxicity were observed when mice were treated with extract dose up to 2000 mg/kgb.w. A chemical analysis of the extract allowed the identification of phenolic compounds as the major components. Glycosylated quercetin, amentoflavone derivate and a tetramer of proanthocyanidin were identified by liquid chromatography coupled to mass spectrometry. The level of total phenolics in the extract was evaluated at 35.5% and flavonoid content was 2.58%.