Late aneurysm formation in the proximal aorta or distal aortic arch is a recognized sequela of untreated stenosis of the aortic isthmus and is associated with substantial risk of aortic rupture. We describe the case of a 44-year-old man with untreated coarctation of the aorta who presented with a prestenotic dissecting thoracic aortic aneurysm. He declined surgery because he was a Jehovah's Witness. Instead, we performed emergency endovascular aortic repair in which 2 stent-grafts were placed in the descending aorta. Our experience suggests that this procedure is a useful and safe alternative to open surgery in patients who have aneurysms associated with coarctation of the aorta.