Osteosarcoma as a secondary malignancy after hematopoietic stem cell transplantation (HSCT) is very rare. We present a case and review of 18 other cases reported to date. Our patient underwent HSCT for myelodysplastic syndrome at the age of 4 years. She developed osteosarcoma 13 years later. She underwent surgery after three courses of neoadjuvant chemotherapy followed by chemotherapy and mifamurtide. She has no evidence of disease 28 months after termination of chemotherapy. In 18 other cases of secondary osteosarcoma in the literature, 15 had received total body irradiation, eight had received alkylating agents, and six had received etoposide. The median interval from HSCT to the onset of osteosarcoma was 6.5 years (range 2.5–15.3), which confirms that children undergoing HSCT should be followed up for many years. In conclusion, osteosarcoma must be included in the differential diagnosis among solid tumors that may develop following HSCT.