Traumatic subclavian artery injury--a complication of a fracture of the first rib--often occurs immediately after the injury. We, however, experienced a case where a subclavian artery injury developed 36 hours after injury; it was successfully treated by endovascular treatment. The patient was a 60s-year-old female, who was transported to the hospital following a traffic accident. She had multiple right rib fractures, right pneumothorax, left first rib fracture, and pelvic fracture. A thoracic drain was inserted for the right pneumothorax and external fixation was performed on the pelvic fracture, and the patient was hospitalized. Thirty-six hours after the injury, pain and swelling around the left clavicle suddenly appeared without any trigger, followed by shock and respiratory failure. After the patient' s hemodynamics stabilized with rehydration, contrast-enhanced CT was performed. A left hemothorax and a left subclavian artery injury near the first rib fracture were observed. A thoracic drain was placed for the left hemothorax, and an endovascular stent graft was placed in the subclavian artery injury. Subsequently, her condition stabilized, and she was discharged from the ICU 14 days after the accident. If the sharp fractured end of the first rib is located near the subclavian artery, subclavian artery injury may occur later and should be monitored carefully.