Collagenous gastritis, a counterpart of collagenous colitis, is an extremely rare disorder. The first case of collagenous gastritis in a Korean boy in his pre-teens who had been receiving treatment for refractory iron deficiency anemia has been reported. The patient had been suffering from intermittent abdominal pain, recurrent blood-tinged vomiting and poor oral intake. The gastric endoscopy revealed diffuse cobble-stone appearance of the mucosa with easy touch bleeding throughout the stomach but no abnormalities in the esophagus, duodenum, and colon. Pathologic examination of the gastric biopsies from the antrum, body and cardia showed a subepithelial collagen deposition with entrapped dilated capillaries, moderate infiltrates of lymphoplasma cells and eosinophils of the lamina propria, and marked hypertrophy of the muscularis mucosa. The collagen deposition appeared as discontinuous bands with focally irregular extension into the deeper part of the antral mucosa. It measured up to 150 μm. Helicobacter pylori infection was not detected. The biopsies from the duodenum, esophagus and colon revealed no pathologic abnormalities.