We reported a rare case of iatrogenic aortic dissection caused by incorrect frozen elephant trunk (FET) deployment. A 53-year-old man underwent total arch replacement with FET for aortic arch aneurysm and concurrent PAU in the descending aorta. However, after FET deployment, aortic dissection occurred. We analyzed that the tip of FET stent had been inserted into the PAU and caused aortic dissection. We performed some salvage procedures. However, the patient died on the 1st postoperative day. Therefore, care should be taken to avoid incorrect deployment of FET when there is a large tear or ulcer lesion in the proximal descending aorta.