During cancer progression, malignant cells may evade immunosurveillance. However, evidence for immunological escape in humans is scarce. We report here the clinical course of a melanoma patient whose initial tumor was positive for the antigens NY-ESO-1, MAGE-C1, and Melan-A. Upon immunization with a recombinant vaccinia/fowlpox NY-ESO-1 construct, the patient experienced a mixed clinical response and spreading of the NY-ESO-1 epitopes in the CD4+ T cell compartment. After NY-ESO-1 protein+ CpG immunization, the patient’s anti-NY-ESO-1 IgG response increased. Over the following years, progressing lesions were resected and found to be NY-ESO-1-negative while being positive for MAGE-C1, Melan-A, and MHC-I. The fatal, inoperable brain metastasis was analyzed after his death and also proved to be NY-ESO-1-negative, while being positive for MAGE-C1 and Melan-A, as well as MHC-I. We propose that cancer control and cancer escape in this patient were governed by NY-ESO-1-specific immunological pressure. Our findings provide evidence for the existence of immunoediting and immunoescape in this cancer patient.