We describe a 58-year-old woman who was incidentally found to have gastric and colonic polyposis, hypoalbuminemia, cutaneous hyperpigmentation and onychodystrophy (Cronkhite-Canada syndrome). Histology of polyps from the stomach showed features of juvenile or retention type (hamartomatous) polyps with Helicobacter pylori (H. pylori) infection. The large pedunculated colonic polyps showed hamartomatous polyps with adenomatous component and polypectomy was performed. After the treatment with H. pylori eradication and omeprazole, the gastric polyposis, hypoalbuminemia and anemia regressed, and endoscopic polypectomy of gastric polyps were performed. After the continuous use of omeprazole for 14 months, the patient showed complete resolution of clinical features of Cronkhite-Canada syndrome. The experience of this case suggests that eradication of H. pylori and proton pump inhibitor treatment might be considered in patients with gastric polyposis combined with Cronkhite-Canada syndrome.