Traumatic rupture of the thoracic aorta is extremely rare in pediatric patients. We present a case of blunt traumatic aortic disruption in a 13-year-old boy who was successfully managed by patch aortoplasty using cardiopulmonary bypass. He was involved in a motor vehicle accident. He had a transient loss of consciousness. Initial vital signs were stable. Upon arrival at our hospital he was awake, alert, and oriented. Chest roentgenogram showed a subtly widened upper mediastinum with left pleural effusion. Chest computed tomography revealed a hematoma around the transverse and proximal descending thoracic aorta, and a 25-mm pseudoaneurysm with the intimal flap in the proximal descending thoracic aorta. Aortography verified a partial transection of the proximal descending aorta. Within 4h after injury, aortic repair was initiated through a left anterolateral thoracotomy. Following heparinization, partial cardiopulmonary bypass was established via the right femoral artery and vein. Sequential occlusion of the left subclavian artery, aortic arch between the left carotid and subclavian arteries, and descending aorta was performed. The periaortic hematoma was incised longitudinally to show a transverse tear involving the anterolateral aortic wall 3cm distal to the origin of the left subclavian artery. The disruption involved approximately 90% of the circumference of the aortic wall and there was retraction of the torn edges. A half of the impaired aorta was sutured, primarily to accommodate future aortic growth, and the other half of the defect was closed with a prosthetic patch. Bypass time was 173min. The postoperative course was complicated by persistent low-grade fever and hoarseness. Four years following discharge, he was well with only slight hoarseness, and magnetic resonance angiography two years later demonstrated a normal aorta without clinical evidence of coarctation.