We herein present the first reported case of reversible cerebral vasoconstriction syndrome (RCVS) in Takayasu's arteritis (TA), in a patient with severe thunderclap headache and generalized tonic-clonic seizure. Magnetic resonance imaging and angiography revealed posterior reversible encephalopathy syndrome, followed by severe vasoconstriction in multiple arteries. RCVS should be included in the differential diagnosis of thunderclap headache attacks with radiologic intracranial vascular abnormalities in connective tissue diseases, including TA.