Reversible cerebral vasoconstriction syndrome (RCVS) is a rare cerebrovascular disorder affecting large- and medium-sized arteries, occurring most commonly in young women. Thunderclap headache is the usual primary symptom; seizure is uncommon. During the postpartum period, seizure is a significant concern. The main causes of postpartum seizures are posterior reversible encephalopathy syndrome and cortical venous thrombosis; RCVS-related postpartum seizure is rare. Despite its rarity, its course may be fulminant, resulting in permanent disability or death if the diagnosis is delayed and treatment is not started promptly. We report an unusual case of RCVS presenting as a subarachnoid hemorrhage in a 31-year-old woman admitted for postpartum seizure.