We report a case of a 2-year-old boy with Down syndrome complicated by Moyamoya syndrome who developed extensive multiple cerebral infarction after status epilepticus on the third day of a measles infection. MR angiography revealed the occlusion of the terminal portion of the bilateral internal carotid artery and the basilar artery. Fever, dehydration, activation of coagulation associated with the infection, relatively decreased cerebral blood flow during status epilepticus, and central nervous invasion of the measles virus may have played a role in the development of the infarction. Moyamoya like cerebrovascular lesions occur more often and is more aggressive in children with Down syndrome than in the general pediatric population, and their clinical presentation is always the infarction type. In patients with Down syndrome complicated by Moyamoya syndrome, an early diagnosis and prevention of infarction are important.