Vascular lesions of the duodenum, including hemangioma, are rare causes of gastrointestinal bleeding. We herein describe a 52-year-old woman with a solitary cavernous hemangioma of the duodenum that caused chronic gastrointestinal bleeding. Repeated upper gastrointestinal endoscopy and a barium meal study revealed a solitary vascular tumor in the fourth portion of the duodenum, although the initial investigations including selective angiography were unsuccessful. A wedge resection of the duodenum was performed and microscopical examination showed a cavernous hemangioma. Vascular lesions should therefore also be considered in the differential diagnosis of patients with gastrointestinal bleeding of unknown origin.