A man in his 50s was injured in a traffic accident. Computed tomography showed bilateral traumatic pneumothorax, pelvic fractures, and left common carotid artery occlusion. Fourteen hours after admission, right hemiplegia and deterioration of consciousness suddenly appeared, and magnetic resonance imaging showed cerebral infarction. Anticoagulant therapy was started after surgery for the pelvic fracture, and neurological symptoms did not progress. Traumatic common carotid artery occlusion is very rare. Administration of anti-platelet drugs has been reported as useful, but is often difficult in polytrauma patients. Further study is needed regarding optimal treatment in the future.