Background: Gastric ulcers brought on by stress offer an intriguing area of study. The persistent challenges in properly controlling and treating these ulcers have attracted a lot of research interest. The primary biologically active ingredient in freshly crushed garlic extract is thought to be allicin. Research has demonstrated that allicin possesses antibacterial, antioxidant, and anti-inflammatory qualities. Objective: To determine any potential underlying processes and assesses the gastroprotective impact of allicin on immobilization stress-induced stomach ulcers. Material and Methods: Three groups of thirty male rats were created: control, ulcer, and ulcer+allicin (10/group). The following factors were assessed: gastric ulcer index values, stomach pH, serum corticosterone, body weight change, stomach PGE2, stomach MDA, stomach GSH, stomach TNF-α, stomach IL-10, and the expression of Nrf2 and HO-1 genes in the stomach. Additionally, stomach tissue was evaluated by histopathology and COX2 immunohistochemistry. Results: Compared to control the ulcer group exhibited dramatically lower change in BW, gastric pH values, gastric GSH, gastric PGE2, gastric IL-10 and gastric gene expression of Nrf2 and HO-1, while also exhibiting significantly higher serum corticosterone, gastric ulcer index values, gastric MDA and gastric TNF-α together with upregulation of COX2 immunoreaction compared to control. Allicin dramatically improved stress-induced changes in gastric tissue. Conclusion: Through the upregulation of the Nrf2/HO-1 signaling pathway, as well as its anti-inflammatory and antioxidant properties, allicin provides gastroprotective effects to rats with stress-induced stomach ulcers.