Hemorrhage through the pancreatic duct into the duodenum, so called "hemosuccus pancreaticus", is a rare cause of gastrointestinal bleeding with diagnostic difficulties. We report a 60-year-old man with recurrent upper gastrointestinal bleeding due to rupture of a splenic artery pseudoaneurysm into the pancreatic duct. Initial upper gastrointestinal endoscopy failed to identify the site of the hemorrhage. Abdominal computed tomography disclosed a cystic mass containing a well-enhanced spherical area at the pancreatic tail. Arterial blood flow was demonstrated in the lesion by Doppler ultrasound. Celiac angiography demonstrated a saccular pseudoaneurysm arising from the splenic artery. Bleeding from the ampulla of Vater located in a big duodenal diverticulum was found on repeat endoscopy. Surgical resection of the pseudoaneurysm with distal pancreatectomy and splenectomy was successfully performed. The patient remained symptom-free 5 months after the operation. Hemosuccus pancreaticus, although rare, remains important in the differential diagnosis of upper gastrointestinal bleeding of obscure origin.