A 23-year-old man was admitted because of polydipsia and polyuria. As chest radiographs and computed tomography showed mediastinal and bilateral hilary lymph node swelling, and diffuse small nodules in bilateral lung fields, we suspected sarcoidosis. Sarcoidosis was diagnosed by biopsy of a cervical lymph node, and central diabetes insipidus was diagnosed by fluid restriction test and vasopressin load test. A pituitary mass was also revealed by magnetic resonance imaging. Prednisolone therapy improved all of his clinical findings except diabetes insipidus. He had to continue intranasal 1-desamino-8-D-arginine vasopressin (DDAVP) therapy.