Gastric ulcer affects people worldwide, and its inefficacy and recurrence have fueled the search for new therapeutic strategies. Despite the well-known use of allantoin in medicines and cosmetic products, its effect has not yet been studied with regard to gastric ulcer. Hence, the aim of the present study was to explore the pharmaco-mechanistic efficacy of allantoin against commonly harmful agents that cause injuries to the stomach. Ethanol, indomethacin, and stress-induced gastric ulcer models were adopted, in addition to pylorus ligature, a quantification of vascular permeability, glutathione (GSH), gastric adhered mucus, prostaglandin (PGE), pro-inflammatory cytokines levels, myeloperoxidase (MPO), and catalase (CAT) activities. The gastric lesions were examined by gross, histological, and ultrastructural features. The results showed that treatment with allantoin (60mg/kg, per oral) reduced the gastric ulcer formation in all models. Furthermore, allantoin reduced the parameters of gastric acid secretion and attenuated both the vascular permeability and MPO activity. The levels of pro-inflammatory cytokines were also reduced, accompanied by a restoration of CAT activity and GSH levels. Notably, allantoin treatment preserved the gastric-adhered mucus and PGE levels after ethanol administration. Microscopic and ultrastructural analysis revealed that allantoin maintained tissue integrity and prevented morphological changes in cells caused by ethanol. In summary, we demonstrated for the first time that allantoin possesses gastroprotective activity through anti-inflammatory, anti-oxidative, antisecretory, and cytoprotective mechanisms. The antisecretory and cytoprotective mechanisms are probably associated with an increase in PGE levels.