Lymphocytic hypophysitis (LyH) is an uncommon intrasellar lesion characterized by lymphocytic infiltration of the adenohypophysis. Evidence suggests that the cause is autoimmune, and the symptoms are usually related to either a mass effect or endocrine dysfunction. Lymphocytic hypophysitis has been described rarely in the setting of other simultaneous pathological processes that involve the pituitary and sella turcica, and is postulated to arise from an intrinsic inflammatory response. The authors report the case of a 43-year-old woman who presented with a 2-month history of galactorrhea and pseudohyperprolactinemia secondary to a 10-mm lesion within an enlarged pituitary gland. She was nulliparous and had no contributory medical history. Serial neuroimaging performed over a 2-year period demonstrated lesion growth, and visual deficits had developed; together these warranted surgical intervention. A transsphenoidal resection was performed. Microscopic and immunohistopathological examinations revealed a nonsecreting pituitary adenoma with concurrent lymphocytic adenohypophysitis. This is the first documented case of LyH in the setting of a null-cell pituitary adenoma. The authors review the related literature and outline potential mechanisms for the concurrent development of LyH and a pituitary adenoma.