An association between Crohn's disease and gastric cancer has not been clearly defined. A 34-year-old man was referred to our hospital for the evaluation of a gastric lesion and treatment of small-bowel Crohn's disease. We diagnosed the gastric lesion as adenocarcinoma, using endoscopy and histological studies. The patient underwent a distal gastrectomy, with well-differentiated adenocarcinoma being found; partial resection of the small bowel was also performed because of an entero-enteric fistula. His postoperative course was uncomplicated.