A 56-year-old woman presented with sudden-onset headache and nausea. She was transferred to our hospital from a local hospital after subarachnoid hemorrhage and unilateral moyamoya disease were diagnosed by computed tomography and magnetic resonance angiography. On admission, she showed no disturbance of consciousness or neurologic deficits. Cerebral angiography showed an anterior communicating artery aneurysm (3 mm in maximum diameter), stenosis at the end of the right internal carotid artery,

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... and abundant ipsilateral moyamoya vessels. On the same day, endovascular embolization was performed using six coils, and the aneurysm was completely occluded with preservation of the parent artery. After embolization, neither symptomatic cerebral vasospasm nor hydrocephalus occurred. The patient was discharged without neurologic deficits. According to several reports, it is difficult to perform direct surgery for a ruptured aneurysm associated with moyamoya vessels because of technical difficulties attributable to the abundance of collateral vessels in the operative field and postoperative cerebral ischemia due to collateral vessel injury. Endovascular embolization for an anterior communicating artery aneurysm associated with unilateral moyamoya disease is a good option for cases in which direct surgery is difficult.