Collision tumors is rare entities in which two distinct primary tumors develop in contiguity. They may arise as independent tumors in the same organ or in adjacent organs. The occurrence of a collision tumor in the stomach, consisting of adenocarcinoma and neuroendocrine tumor, is extremely rare. We report a case of a patient, who had undergone a radical subtotal gastrectomy for gastric cancer 3 year earlier, and an ulcerating tumor of the gastric stump had developed. A total resection of the remnant stomach was performed, and the pathological examination revealed a collision tumor consisting of an adenocarcinoma and a neuroendocrine tumor. The coexistence of both adenocarcinoma and neuroendocrine tumor of the gastric stump has never been reported. The authors present this case and a review of the relevant literature.