Staged repair of extensive thoracic aortic aneurysms puts certain patients at risk of rupture. We report the case of a patient with Marfan syndrome who presented with subacute type-A aortic dissection and a large descending aortic aneurysm. We used the arch-first technique with a commercially available Dacron T-graft. A clamshell incision was used for exposure. A button of arch vessels was anastomosed to the T-graft. Antegrade cerebral perfusion was established through the side branch. The distal end of the graft was anastomosed to the descending aorta and the proximal end to a composite graft. The duration of cerebral ischemia was 30 minutes; antegrade cerebral perfusion lasted 52 minutes. The patient experienced no neurologic dysfunction and was discharged with no major deficit. This technique shortens brain-ischemia time and is a good option if the risk of rupture of the descending component of an extensive thoracic aortic aneurysm is high.