Abstract: Background: Mosapride, a gastroprokinetic agent that acts as a selective 5HT4 agonist, is used for the treatment of gastritis, gastro-oesophageal reflux disease, functional dyspepsia and irritable bowel syndrome. Non-steroidal anti-inflammatory drug (NSAID) commonly used as a prescription medication to reduce fever, pain, stiffness, and swelling. Peptic ulcer is a major side effect of NSAIDs. In this study we tested the effect of oral administration of mosapride 0.25, 0.5, 0.75, 1.25, 2.5 and 5mg/kg on gastric mucosa and on NSAIDs induced gastric ulcers in rats. Methods: Acute gastric ulcers were induced in rats by the oral administration of indomethacin. Results: Mosapride had no effect on gastric mucosa but increased the prostaglandin E2 (PGE2) level. Pretreatment with mosapride at 0.25 and 0.5 mg/kg prevented the mucosal damage induced by indomethacin. The higher doses, from 0.75 up to 5mg/kg, had no effect on indomethacin-induced gastric ulcer. Conclusion: Mosapride had no effect on gastric mucosa but increased PGE2 and demonstrated anti-ulcer effect in small doses only. This effect could be partially mediated through increased prostaglandin E2.