Ipilimumab (YERVOY) is a monoclonal CTLA-4-antibody with anti-tumor-immunogenic effect and is used to treat malignant melanoma. In this case study, we present [18F]Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) images of a 37-year-old woman with metastatic melanoma, who was previously treated with interferon-alpha therapy and dacarbazine and still progressed. After four cycles of ipilimumab, there was a complete remission of the disease with no evidence of vital, FDG-positive tumor tissue. The follow-up for a total of 1 year confirmed the therapeutic success. This report demonstrates that FDG-PET/CT is a reliable imaging method for response monitoring in metastatic melanoma treated with ipilimumab.