Inflammatory myofibroblastic tumor (IMT) is an uncommon lesion with variable clinical behaviors from benign to mimicking malignant tumors. On rare occasions, IMT may exhibit malignant transformation, and the strategy of malignant IMT is remained undetermined. Herein, we report an extremely unusual case of IMT with malignant transformation of the urinary bladder in a 14-year-old boy characterized by local aggressive behavior and was successfully treated by combined surgery and perioperative chemotherapy.