A 4-year-old girl was admitted to our department with the complaints of severe headache, nausea, vomiting, and photophobia. She had a 1-year history of migrainelike headache that occurred every 1 to 2 months. Her neurologic examination was normal, but T-weighted axial magnetic resonance imaging (MRI) of the brain showed flow void within the basal ganglia owing to parenchymal vascular collaterals. Magnetic resonance angiography and digital substraction carotid angiography showed both occlusion of the internal carotid artery in the supraclinoid portion and extensive parenchymal vascular collaterals. Because there was no evidence of risk factors for cerebral arterial occlusion and cerebral infarct or hemorrhage, she was diagnosed as having moyamoya disease. In any case of atypical migrainelike headache, a detailed investigation should be kept in mind to detect an underlying vascular disease such as moyamoya.