The present study was carried out to investigate antiulcer activity of aqueous extract of bark of Alphitonia zizyphoides (Sprenger) A. Gray (Family: Rhamnaceae) in ethanol and indomethacin induced ulceration in the albino rats. Preliminary aqueous extract of bark of Alphitonia zizyphoides was subjected to the acute oral toxicity study according to the OECD guideline no. 425. Based on which, two dose levels i.e. 200 and 400 mg/kg were selected for the further study. Ulcer index and percentage inhibition of ulceration was determined for ethanol and indomethacin induced ulcer model. Omeprazole at 20 mg/kg was used as the standard drug. Pretreatment of aqueous extract of bark of Alphitonia zizyphoides showed significantly (P<0.05) decrease in number of ulcers and ulcer score index in ethanol and indomethacin induced ulceration models. The aqueous extract of bark of Alphitonia zizyphoides possesses significant antiulcer properties in a dose dependent manner. In conclusion the antiulcer properties of the extract may be attributed to the presence of phytochemicals like flavonoids and tannins present in the plant extract with various biological activities.