We previously profiled the chemical composition of wax apple, Syzygium samarangense, leaf extract using HR-LC-MS/MS and reported its antioxidant, hepatoprotective and antitrypanosomal activities. The plant is widely used in traditional medicine to cure several ailments like bronchitis, asthma, diabetes, fever, pathogenic infections, gut spasms, as well as renal diseases. However, neither the gastroprotective effects nor the underlying mechanisms were explored. Here, we investigated the gastroprotective potential of the leaf extract on indomethacin-induced gastric ulcer in rats and explored the involved mechanism(s) of action. Administration of indomethacin significantly increased the ulcer index, mucosal injury, the gastric levels of the inflammatory markers nuclear factor kabba B-p65(NF-κB p65), myeloperoxidase (MPO), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), lipid peroxidation product, malondialdehyde (MDA) and Caspase-3 expression. It reduced the gastric levels of the endogenous antioxidants glutathione as well peroxidase (GPx), reduced glutathione (GSH) and the gastric mucosal protective factors, mucus secretion and goblet cells. Pretreatment with the leaf extract displayed a prominent decrease in the ulcer index, inflammatory cell infiltration, inflammatory markers, MDA, protein expression of Caspase-3 and a significant increase in the gastric levels of the endogenous antioxidants, mucus content and goblet cell proliferation when compared to the indomethacin group. The individual secondary metabolites of the extract exhibited low binding energy when docked into the prostaglandin receptors EP3 and EP4. This study revealed the gastroprotective effect of S. samarangense on indomethacin-induced gastric ulcer in rats. The gastroprotective effects might be attributed to cytoprotective, antioxidant, anti-inflammatory and antiapoptotic activities with a possible potential of activating EP3 and EP4 receptors. In conclusion, S. samarangense has a promising potential in the prevention of NSAIDs-induced ulcers.