A 38-year-old man presented with typical symptom of acute pericarditis and chronic cardiac tamponade 6 weeks after blunt trauma. Follow-up computed tomography after 2 weeks revealed a localized dissection at the proximal part of the ascending aorta. This is a rare case of chronic Stanford type A aortic dissection after blunt trauma, a diagnosis of which was established later with consistent suspicion and repeated examination by computed tomography.