Patients with relapsed stage 4 neuroblastoma have an extremely poor long-term prognosis, making the investigation of new agents of interest. We report the outcome of the first patient treated in a phase 1 study for relapsed neuroblastoma, using the chemotherapy agent decitabine to upregulate cancer testis antigen expression, followed by a dendritic cell vaccine targeting the cancer testis antigens MAGE-A1, MAGE-A3, and NY-ESO-1. Our patient had persistent tumor in his bone marrow after completion of standard therapy for neuroblastoma, including multiagent chemotherapy, tumor resection, stem cell transplantation, radiation therapy, and anti-GD2 monoclonal antibodies. His marrow disease persisted despite chemotherapy, which was given while the vaccine was being produced. After 3 cycles of decitabine and vaccine, this patient achieved a complete remission and is now 1 year from his last treatment, with no evidence of tumor in his bone marrow or other sites. This patient was noted to have an increase in MAGE-A3–specific T cells. This is the first report combining demethylating chemotherapy to enhance tumor antigen expression followed by a cancer antigen vaccine.