We report herein a case of successfully treated advanced, nonfunctioning islet cell carcinoma associated with left-sided portal hypertension. The splenic vein was obstructed by a huge intravenous tumor thrombus developing from the main pancreatic tumor. Direct invasion to adjacent organs such as the spleen, colon, left kidney and stomach was also observed, although liver metastasis was not present. Radical resection was carried out with removal of these five involved organs and the patient is alive without recurrence more than 5 years after surgery.