We report a rare drugs adverse effect of a GLP1-RA, presenting as severe gastric stasis, eosinophilic duodenitis, and high bowel obstruction. The patient, treated with oral semaglutide for type 2 diabetes and obesity, developed progressive upper gastrointestinal symptoms culminating in faecal vomiting. Endoscopic and histological findings revealed marked eosinophilic infiltration of the duodenum. To our knowledge, this is the first reported case linking semaglutide to eosinophil-driven duodenitis causing mechanical obstruction. As the use of GLP1-RAs expands, clinicians should be aware of rare but potentially serious gastrointestinal adverse effects, particularly in patients with risk factors for impaired motility. Early recognition of symptoms and consideration of underlying eosinophilic gastrointestinal disease are essential for timely diagnosis and management.