A man in his 60s with no obvious trauma experienced sudden left-sided weakness and confusion. At a local hospital at 4.5 hours after onset, a cranial CT was unremarkable; the initial diagnosis was acute ischemic large artery stroke. He was transferred to our stroke center for mechanical thrombectomy within 6 hours. Digital subtraction angiography revealed no appearance of left common carotid artery and left subclavian artery, accompanied by suspicious protrusion of aortic false lumen (figure, A, arrows). Aortic dissection was suspected and confirmed by CT angiography (figure, B and C), with emergent surgery following. Painless long-segmental aortic dissection should be considered during evaluation for IV thrombolysis and mechanical thrombectomy.