We report an asymptomatic 72-year-old woman with a small, incidentally detected, pancreatic somatostatinoma. The tumor, measuring 1 cm in diameter, showed a hypervascular pattern of contrast enhancement on computed tomography, and was found angiographically to receive a blood supply from the posterior superior pancreaticoduodenal artery. The results of preoperative hormonal assays all were normal. No assay for somatostatin was performed. No abnormality in either the pituitary or parathyroid was found. We thus considered the tumor to be a sporadic, nonfunctioning endocrine cell tumor, and enucleation was carried out. As some tumor cells in the resected specimen showed immunoreactivity for somatostatin, a diagnosis of somatostatinoma was made. Therefore, the possibility of somatostatinoma should be kept in mind when making a differential diagnosis of pancreatic endocrine tumors in cases where even a small hypervascular tumor is detected on enhanced computed tomography.