We report the case of a 17-year-old Korean girl with systemic lupus erythematosus (SLE) who presented with sudden weakness of the right-sided extremities and dysarthria. Oral prednisolone was being taken to control SLE. Results of clinical and laboratory examinations did not show any evidence of antiphospholipid syndrome or thromboembolic disease nor SLE activity. Cerebral angiography showed stenosis of the left internal carotid artery and right anterior cerebral artery with accompanying collateral circulation (moyamoya vessels). After the patient underwent bypass surgery on the left side, she recovered from the neurological problems and did not experience any additional ischemic attack during the 14-month follow-up period. This case represents an unusual association between moyamoya syndrome and inactive SLE (inactive for a relatively long interval of 2 years) in a young girl.