Lymphocytic hypophysitis (LYH) is a chronic inflammation that primarily affects the pituitary gland. This disorder has recently been classified into lymphocytic adenohypophysitis (LAH), lymphocytic infundibulo-neurohypophysitis (LINH), and lymphocytic infundibulo-panhypophysitis (LIPH) according to the affected area. We report a case of LINH in a 68-year-old woman who presented with diabetes insipidus (DI). In this case, the posterior lobe was affected in both endocrinological assessment and magnetic resonance imaging (MRI) findings. In contrast, the anterior pituitary was not affected in endocrinological assessment but was affected in MRI findings. Indeed, the patient did not develop hypopituitarism. We believed that these clinical and radiological features were unique in regard to the classification of LYH. To confirm the classification of LYH and the distinction from pituitary adenoma, a pituitary biopsy was performed. Based on the pathological and endocrinological assessment, the patient's disorder was finally diagnosed as a variant of LINH. Current evidence recommends that surgical intervention for LYH should be avoided because the natural course of LYH is essentially self-limiting. Therefore, the accumulation of the knowledge of many variants of LYH is important for the preoperative differential diagnosis of pituitary masses. Our clinical observation could be useful for avoiding unnecessary surgical intervention.