Objective(s): Some species of Prunus L. are popularly used to treat gastric ulcers. However, the possible healing mechanisms of the anti-ulcer activity of P. spinosa, which has proven antioxidant, anti-inflammatory, and wound-healing properties, are unclear. Materials and Methods: Ethanol extracts of P. spinosa fruits were administered orally at 100 mg/ kg and 200 mg/kg to Wistar albino rats, with an indomethacin-induced gastric ulcer model. The ulcerous areas on the stomach surface were examined macroscopically. Tissues were examined histopathologically and biochemically. LC-HRMS revealed the phytochemical content. Results: TNF-α, IL-6, IL-1β, IL-8, and NF-kB levels were higher in the gastric ulcer group than in the extract groups. The VEGF values did not differ in each group. A significant difference was found between the lansoprazole group and the high-dose P. spinosa group regarding PGE2 levels. A histopathologically significant difference was observed between the healthy group and the indomethacin-applied groups in terms of neutrophilic infiltration of the gastric mucosa. Ascorbic acid (1547.521 µg/g), homoprotocatechuic acid (1268.217 µg/g), and genistein (1014.462 µg/g) were found as the main compounds in the P. spinosa extract by LC-HRMS. Conclusion: Our results demonstrated that P. spinosa protected the gastric mucosa from inflammation and also modulated the PGE2 pathway. When considered in terms of TNF-α, IL-1β, IL-8, IL-6, PGE2, and NF-kB values, it can be concluded that it has a similar or even more positive effect than the reference substance. P. spinosa showed its effects in a dose-dependent manner.