The surgical treatment of malignant bone tumors involving the pelvis represents a great challenge in terms of local control. Internal hemipelvectomy is a major surgical procedure that involves the resection of the entire hemipelvis or of a portion of the hemipelvis with preservation of the ipsilateral extremity. The need for a bilateral internal hemipelvectomy is an extraordinary situation. We describe the case of an 11-year-old girl with a primary diagnosis of rhabdomyosarcoma of the bladder at the age of two years who subsequently developed a right pelvis osteosarcoma at the age of six years and a left pelvis osteosarcoma at the age of nine years. She ultimately underwent sequential bilateral internal hemipelvectomies and she postoperatively ambulates without an assist device.