To report a case of ruptured aneurysm caused by an endoleak 29 months after transluminal endovascular grafting (TEG) for a dissecting aortic aneurysm.We performed TEG with the use of a stent graft in a patient with a DeBakey type III chornic aortic dissection. The primary entry in the descending thoracic aorta was successfully sealed, and the false lumen was thrombosed. However, a new endoleak developed in the false lumen of the proximal portion of the stent graft 29 months after TEG. The aneurysm ruptured at the site; the patient underwent urgent surgery and survived.The endoleak may have been caused by insufficient radial force of the stent graft. Further investigation is needed to evaluate the structures and shapes of stent grafts providing suitable radial force for placement in the true lumen of the aorta, the diameter of which changes after stent-graft placement.