Somatostatin secreting islet cell adenoma(somatostatinoma) of the pancreas is a rare entity. Less than 30 cases of pancreatic somatostatinoma could be searched in the world literature. We present a case of somatostatinoma of the pancreas in a 64-year-old woman. This patient had suffered from diabetes, cholelithiasis and intermittent diarrhea. Laboratory examination revealed steatorrhea, blood somatostatin level of 30 pg/ml, and fasting blood glucose level of 116 mg/dl. Subtotal pancreatectomy was done after radiological demonstrations of a round tumor mass in the pancreas. It was a 2 cm-sized well demarcated yellowish brown round solid mass located in the proximal pancreas. A retention cyst was seen just distal to the tumor. Histologically, tumor masses consisted of polygonal cells with distinct cell border, having granular eosinophilic cytoplasm and small bland looking nuclei. The tumor cells were arranged in small solid islands and trabeculae, separated by fibrovascular stroma. Immunohistochemical stain for somatostatin was positive in the cytoplasm of the individual tumor cell, and ultrastructurally variable sized membrane bound electron dense granules of 200 nm in average diameter were found in tumor cells.