About half of osteosarcomas occur near the knee joint, but other sites such as the humerus, upper femur, fibula, spine, and ilium can also occur. However, rib osteosarcoma is rarely reported. Here, we report the case of a 17‐year‐old female who was found to have a left dorsal mass on physical examination. Computed tomography (CT) revealed bone destruction in the seventh rib, leading to surgery for mass excision. Pathological results suggested chondroblastic osteosarcoma. After surgery, the patient was treated with chemotherapy and is doing well.