We report the first case of a tumor of the Ewing sarcoma family of tumors arising from the urinary bladder 3 years after chemotherapy for acute lymphoblastic leukemia. A 16-year-old boy complained of macrohematuria and dysuria during the posttreatment follow up of his acute lymphoblastic leukemia. Ultrasonography and computed tomography revealed a I-cm sized intravesical tumor. The tumor was transurethrally resected with no residual tumor at the margin. Histopathologic analyses revealed a small round blue cell tumor with positive staining for CD99(MIC2) antibody. EWS-FLI1 fusion transcripts were detected in the tumor tissue by reverse transcriptase polymerase chain reaction. These findings support the diagnosis of Ewing sarcoma family of tumor. After adjuvant multidrug chemotherapy, the patient has shown no evidence of disease for more than 2 years.