In the Nara Period, Kukai opened the Shingon sect within the temple and in the Heian Period, together with the Tendai-shu sect brought by Saicho, Todai-ji became a 'Hasshu Kengaku no tera' (Temple of syncretic study of eight sects of Buddhist learning).
平安時代には空海によって寺内に真言院が開かれ、空海が伝えた真言宗、最澄が伝えた天台宗をも加えて「八宗兼学の寺」とされた。