In the present study antioxidant and antiulcer potential of Citrullus lanatus seeds were evaluated. Antioxidant activity of all the extracts (chloroform, ethylacetate and methanol) was measured by DPPH method. Methanolic extract of Citrullus lanatus (MECL) seeds showed maximum antioxidant potential and was evaluated for its anti-ulcerogenic activity by pyloric ligated (PL) and water immersion stress (WIS) induced ulcer models in rat. Gastric volume and free and total acidity were measured in PL model whereas; ulcerative index was measured in both the models at 100, 200 and 300 mg/kg doses of MECL. Rats treated with MECL (300 mg/kg) showed significant decrease in the gastric volume, free acidity and total acidity in case of PL model and showed significant percentage inhibition of ulcer as indicated by decrease in ulcerative index in both the models. The extract of Citrullus lanatus seeds possesses good antioxidant and anti-ulcer activity.