Immunotherapy-induced hypophysitis presents with headache, fatigue, and visual disturbances. The diagnosis is supported by imaging findings of pituitary swelling, enhancement, and hypermetabolism and established by low levels of pituitary hormones. A 64-year-old man with metastatic melanoma on nivolumab presented with a severe headache, initially attributed to sinus disease. Contrast CT was interpreted as minor sinus disease and no pituitary abnormality. Hypophysitis was eventually diagnosed and successfully treated based on PET and laboratory findings. Our retrospective analysis demonstrated abnormal convex superior pituitary border visible on contrast and noncontrast CT and PET. This feature may aid diagnosis in the challenging cases.