We report a very rare case of atypical granular cell tumor arising in the neurohypophysis of a 56-year-old woman. The tumor was seen on radiology to be lobulated, soft and diffusely enhanced, the same as pituitary macroadenoma, but it was anatomically localized within the posterior part of the hypophysis. We partially removed the tumor via the transsphenoidal approach. The pathology showed nuclear pleomorphism, spindling features, and lymphoplasmacytic infiltration. Ki-67 and S-100 protein were focally positive in tumor cells. Histological diagnosis confirmed an atypical granular cell tumor in the sellar region, which is a rare tumor that often has the clinical appearance of a pituitary adenoma. Ophthalmologic symptoms are the most common, followed by endocrinologic manifestations. Here we describe its symptoms and radiological and pathological features.