Langerhans cell histiocytosis (LCH) has diverse clinical manifestations, including intracranial mass lesions. We report a case of LCH that manifested as a suprasellar mass, and initially misdiagnosed as a germ cell tumor. A 29-year-old woman presented with polyuria, polydipsia and amenorrhea. Laboratory findings revealed hypopituitarism with central diabetes insipidus, and a suprasellar mass and a pineal mass were observed on magnetic resonance imaging. Under the clinical impression of a germ cell tumor, the patient was treated with germ cell tumor chemotherapy (cisplatin and etoposide) and radiation therapy without biopsy. After initial shrinkage of the lesions, further growth of the tumor was observed and a biopsy was performed. The histopathology revealed LCH. After chemotherapy according to the LCH III protocol, the tumor disappeared. She is on regular follow up for 5 years without relapse. The present findings indicate that LCH should be included in the differential diagnosis of a suprasellar mass, even in adults, especially when it manifests with diabetes insipidus. This case also underscores the importance of a histopathologic diagnosis in patients with suprasellar tumors before the initiation of a specific therapy, even if the clinical findings are highly suggestive of a specific diagnosis.