Traumatic aneurysm of the brachiocephalic artery is rate. We presented a case of traumatic aneurysm of the brachiocephalic artery caused by traffic accident. A 28-year-old woman suffered a blunt chest trauma. A chest X-ray revealed a widening of the superior mediastinum and multiple rib fractures. CT scanning demonstrated left hemothorax with lung contusion and upper mediastinal hematoma. An aortography was performed which showed aneurysmal dilatation at the origin of the brachiocephalic artery. The patient underwent an operation 24 hours after chest injury. An aorto-right common carotid artery and right subclavian artery bypass with bifurcated Dacron graft was performed while monitoring temporary artery pressure. After resection of aneurysm, We found that about 3 cm longitudinal laceration of intima on the posterior wall of brachiocephalic artery. Her post operative condition was good and no neurological defect was noted.