Hemosuccus pancreaticus is an unusual gastrointestinal hemorrhage through the main pancreatic duct. We report a rare case of hemosuccus pancreaticus due to a simple mucinous cyst of the pancreas. A 52-year-old man who had been followed-up for a suspected branch duct intraductal papillary mucinous neoplasm (IPMN) visited the emergency room due to hematochezia. Endoscopy showed active bleeding from the ampulla. Computed tomography revealed hemorrhage in a 2.0-cm cystic mass in the pancreatic body. The patient was diagnosed with hemosuccus pancreaticus caused by bleeding into the main pancreatic duct from suspected IPMN. Elective laparoscopic distal pancreatectomy was performed. The histopathological diagnosis was a simple mucinous cyst with squamous metaplasia based upon the pathological finding involving the absence of ovarian-type stroma. In conclusion, it should be recognized that a pancreatic cyst including simple mucinous cyst may cause hemosuccus pancreaticus, and these cysts should be viewed as neoplastic and approached similarly as other mucinous pancreatic neoplasms.