We report a rare case of nesidioblastosis and hyperplasia of α cells, microglucagonoma, and nonfunctioning islet cell tumor of the pancreas. The patient's clinical presentation, diagnosis, treatment, pancreas pathology, and follow-up are reviewed. A 60-year-old patient was incidentally found to harbor a pancreatic mass with markedly elevated glucagon levels but without glucagonoma syndrome. She was initially diagnosed with glucagonoma, and the tumor was resected. Pathological examination demonstrated that the tumor was a nonfunctioning islet cell tumor and revealed nesidioblastosis and hyperplasia of α cells and microglucagonoma in the apparently normal surgical margin. The patient still had high postoperative glucagons levels which were suppressed by somatostatin analog treatment. No pancreatic tumors recurred 36 months after surgery. This is the third case of α-cell nesidioblastosis reported in the English literature. Nesidioblastosis and hyperplasia of α cells should be considered in the differential diagnosis of hyperglucagonemia. Somatostatin analog may be used to suppress glucagon secretion in α-cell hyperplasia. © 2008 Lippincott Williams & Wilkins, Inc.