In response to recent changes in the concept and diagnosis of moyamoya disease, we, the Research Committee on Moyamoya Disease have revised the diagnostic criteria for moyamoya disease for the first time in seven years, since 2015. However, since the English version of the previous 2015 diagnostic criteria had not been published, we have recently combined the 2015/2021 revisions into an English version to share the latest information with physicians and researchers around the world involved in basic and clinical research on moyamoya disease.