A 27-year-old woman presented with a history of amenorrhea, visual disturbance, and diabetes insipidus. Magnetic resonance imaging showed a large enhancing suprasellar mass with associated edema involving the left striatum. The lesion was hypometabolic on fluorodeoxyglucose-positron emission tomography. At surgery, a subtotal resection of a vascular tumor that appeared to arise from the posterior pituitary and hypothalamus was carried out. Pathologic examination revealed a granular cell tumor. We report the preoperative neuroimaging findings in this rare posterior pituitary stalk tumor.