A 75-year-old male patient has been followed-up for mixed-type intraductal papillary mucinous neoplasm (IPMN) in the tail of the pancreas for about 20 years. Upon close examination, he was diagnosed of high-risk stigmata due to a nodule having a contrast effect of 5mm or more in the tumor. Based on this, a distal pancreatectomy was performed. Histopathological analysis revealed concomitant IPMN (low-grade) and pancreatic neuroendocrine neoplasm (PNEN) (G1). This prompted us to report a very rare case of coexisting PNEN and IPMN with an interesting pathological finding that might suggest its pathogenic mechanism.