Intensified chemotherapy is one of the strategies currently used in the treatment of children with metastatic Ewing sarcoma. However, the increasing dose intensity has not significantly improved the event-free survival. We report a patient who initially presented with localized Ewing sarcoma and later developed metastatic disease that required dose-intensified chemotherapy. The patient's Ewing sarcoma remained refractory to treatment despite continuous intensified chemotherapy and was complicated by a therapy-related acute myeloid leukemia with 11q23 abnormality. Examination of bone marrow at the last clinical follow up demonstrated both acute myeloid leukemia and residual metastatic Ewing sarcoma.