Osteosarcoma, one of the most common sources of bone malignant tumors, often occurs at the epiphysis, such as in the distal femoral and proximal tibia, but seldom occurs at the costa. Here, we present the case of a 15-year-old girl with giant osteosarcoma on the chest wall. Osteosarcoma is extremely malignant and has a high death rate. We surgically resected the osteosarcoma using cardiopulmonary bypass and administered neoadjuvant chemoradiotherapy.