Somatostatinoma is a very rare neuroendocrine tumor that originates from D cells and accounts for less than 1% of all gastrointestinal endocrine tumors. The duodenum is the most frequent site for this tumor, followed by the pancreas. We here describe a 46-year-old Chinese woman who developed pancreatic somatostatinoma presenting with the characteristic "inhibitory" syndrome, but the symptoms were obscure and seemingly uncorrelated. This case is also unique for its large tumor size and mixed pathological pattern. Distal pancreatectomy was performed, and the patient has remained well since operation. As the syndromes of somatostatinoma may be obscure and atypical, clinicians should review all clinical findings to obtain an accurate diagnosis. Aggressive surgery is preferred to improve the survival.