Lymphocytic hypophysitis is an uncommon autoimmune condition that often results in significant morbidity. Although most cases resolve spontaneously or after a short course of steroids, rarely, refractory cases can cause persistent neurological deficits despite aggressive medical and surgical management. A 41-year-old woman presented with progressive visual loss in the left eye and was found to have a sellar mass. She underwent transsphenoidal surgery because of lesion enlargement. Histopathology was consistent with adenohypophysitis with B-cell predominance. Despite steroid treatment, her neurological condition worsened and she experienced loss of vision in the right eye. Craniotomy with decompression of the right optic nerve was performed. Her condition improved initially, but she continued to have progressive visual compromise over the following months. She was therefore treated with rituximab, a monoclonal antibody against B cells. Her vision improved significantly within a few weeks. There was no clinical or radiographic exacerbation 2 years after starting immunotherapy. Rituximab, an anti-CD20 antibody that specifically depletes B lymphocytes, can be an effective treatment strategy for patients with steroid-refractory, B cell-predominant lymphocytic hypophysitis.