Malignant fibrous histiocytoma, usually seen in patients older than 10 years, is an aggressive soft-tissue sarcoma occurring mostly in the extremities and the trunk, but it is extremely rare in children. We report the clinical, radiological and pathologic features of a five-year-old boy who was diagnosed as a retroperitoneally originated malignant fibrous histiocytoma. The patient with unresectable mass was successfully treated with multidisciplinary approach, with chemotherapy, surgery and radiotherapy, by using combined chemotherapy consisting of vincristine, cisplatinum, adriamycin, cyclophosphamide, actinomycin D and dacarbazine.