Ipilimumab is a human monoclonal antibody directed against a receptor expressed on activated T-lymphocytes (CTLA-4). Binding to this receptor induces T-cell activation against tumor cells. A 77-year-old man with a stage IV metastatic melanoma was treated with ipilimumab. 18F-FDG PET-CT performed for response evaluation revealed intense uptake in the pituitary gland. Two weeks later, biochemical parameters altered confirming hypophysitis. Treatment of the hypophysitis was started, and shortly thereafter, biochemical parameters normalized. Follow-up PET-CT revealed normalization of 18F-FDG uptake in the pituitary gland. In this case, we present a patient with ipilimumab-induced hypophysitis initially diagnosed on 18F-FDG PET-CT.