The present study was designed to investigate the antiulcer activity of ethyl acetate extract of Citrus decumana (grapefruit) peels. The antiulcerogenic activity was evaluated in water immersion and hypothermic restraint stress models at different doses (150, 250 and 350 mg/kg). The antiulcer potential of the extract was assessed by determining and comparing the ulcerative index and biochemical estimation was carried out using various oxidative stress markers i.e., TBARS, GSH, SOD and CAT in the blood and tissue samples. The highest dose (350 mg/kg) of the extract showed significant decrease in the ulcerative index and TBARS level, whereas there was increase in the GSH, SOD and CAT levels. Whereas the lowest and medium dose (150 mg/kg and 250mg/kg) did not produce any significant results. Therefore, our study indicate that the Citrus decumana peel extract may be used as a natural therapeutic agent in the treatment of peptic ulcers.