A 76-year-old woman with serous cystic tumor (SCT) was admitted to our hospital with abdominal pain and was given a diagnosis of severe acute pancreatitis. Infusion of intravenous protein inhibitor and continuous hemodiafiltration (CHDF) were started and she was placed on a respirator, but she died on the 6th day after diagnosis. On autopsy, each SCT cyst showed evidence of hemorrhage. We supposed that the growth of the SCT after hemorrhage compressed the main pancreatic duct and caused severe acute pancreatitis. SCT is benign, and there are no standard treatments. During follow-up of patients with SCT, we should consider the risk of severe acute pancreatitis.