Pancreatic endocrine tumors are rare tumors classified into "functioning" and "nonfunctioning" tumors. A 68-year-old man was admitted to our hospital with the chief compliant of abdominal pain. Various imaging studies demonstrated a mass in the head of the pancreas with intraductal growth into the main pancreatic duct and an intraportal mass. The patient underwent a curative surgical operation. Histopathological examination revealed that it was nonfunctioning endocrine carcinoma of the pancreas. This is the first reported case of a pancreatic endocrine tumor with intraductal growth into the main pancreatic duct and tumor thrombus within the portal vein.