Abstract: Objective To study the clinical characteristics, diagnosis and treatment of malignant islet cell tumor. Methods Twentythree cases of surgery- or biopsy-confirmed malignant islet cell tumor admitted to our hospital from 1993 to 2012 were retrospectively analyzed. Results Of the 23 cases of malignant islet cell tumor, 6 were diagnosed as insulinoma (average diameter 2.1 cm) with their first symptom manifested as Whipple triad or hypoglycemic coma. Single tumor was located in the pancreatic body or tail, 5 were diagnosed as liver metastasis, and 3 underwent tumor resection with their hypoglycemia improved after operation. Of the 23 cases of malignant islet cell tumor, 17 were diagnosed as malignant nonfunctioning islet cell tumor (average diameter 6.2 cm) with their first symptoms manifested as abdominal mass and abdominal pain or painless jaundice. The tumor was located in the pancreatic body or tail of 11 out of the 15 cases of single tumor, 10 cases were diagnosed as liver metastasis and 12 cases underwent tumor resection with their symptoms relieved after operation. The tumor was located in the 23 cases using imaging methods. Conclusion Malignant islet cell tumors mainly include malignant insulinoma and malignant nonfunctioning islet cell tumor, most of which are singly and usually located in the pancreatic body or tail. Its most metastatic site is the liver. Combined treatment, especially surgery, can alleviate the symptoms of hypoglycemia and obstruction.