Objective: To present the case of a 39-year-old male admitted to the hospital with diabetes insipidus as a sequela of a previously undiagnosed diffuse large B-cell lymphoma. This case is unique, as the patient's disease was determined to be an infiltrative malignancy affecting the pituitary infundibular stalk, resulting in multifocal pituitary dysfunction.Methods: Case report.Results: Initially presenting with gastrointestinal bleed, later discovered to be from tumor infiltration of gastric vessels, diagnosis of lymphoma was made when gastrectomy became necessary for hemostasis.