Blunt chest contusion can rarely induce coronary artery dissection with myocardial infarction. Clinical symptoms, electrocardiography, and serial cardiac enzyme evaluations are necessary in patients with thoracic trauma. Angioplasty or bypass surgery is chosen according to the lesion characteristics and associated complications. Here, we report a case of a dissected flap from the left main coronary artery to the left anterior descending coronary artery in a 63-year-old man with acute myocardial infarction secondary to blunt chest trauma during a traffic accident. (J Intern Med Taiwan 2016; 27: 261-266)