A 49-year-old woman underwent upper gastrointestinal endoscopic examination for epigastric discomfort, revealing giant folds on the greater curvature of the stomach. Histological examinations of biopsy specimens taken from the giant folds showed signs of chronic inflammation, and Helicobacter pylori was also identified. She underwent first-step H. pylori eradication. On follow-up endoscopy, H. pylori was not identified. However, endoscopic findings were unchanged and repeated biopsies showed dense infiltration of atypical plasma cells. No proliferation of centrocyte-like cells was seen. Immunohistochemically, plasma cells were positive for lambda-chain. Primary gastric plasmacytoma was diagnosed. Total gastrectomy was carried out with splenectomy and regional lymph node dissection. The patient remains disease free as of 6 years postoperatively.