Currently, radiation therapy is widely used for the treatment and palliation of metastatic bone disease in both adults and children. Recent advances in radiation therapy, such as intensity-modulated radiation therapy, have led to more focused treatments and fewer adverse effects. Although radiation therapy has been associated with several musculoskeletal effects in the growing child, hip dislocation during a course of radiation therapy has not been reported. We report a case of a 12-year-old girl who presented with metastatic bone disease, and developed a hip dislocation during radiation therapy. Possible causes are discussed in detail and a thorough literature review is presented.