Acute aortic dissection presents with a wide range of manifestations. Sometimes an acute coronary syndrome is diagnosed instead of aortic dissection leading to inappropriate treatment. We describe a case of acute aortic dissection with the uncommon involvement of the left main coronary artery. A 64-year-old man was referred to our hospital for primary coronary intervention because ECG demonstrated ST elevation in the aVR lead with diffuse ST-segment depression. Coronary angiography was performed to treat the culprit lesion but the left main coronary artery could not be catheterized. Aortography and transesophageal echocardiography confirmed Stanford type A aortic dissection. The patient died of cardiac arrest in spite of cardiopulmonary resuscitation. This case also illustrates how Stanford type A aortic dissection can present with left main coronary artery obstruction.