Born in 814 in Sanuki Province (Kagawa Prefecture), his mother was a niece of Kūkai. At fifteen he entered Mt. Hiei and studied under Gishin, the first Tendai zasu. In 853 he crossed to Tang China, studying Tendai doctrine and esoteric Buddhism at Tiantai Guoqingsi and Chang'an's Qinglongsi. After returning, he revived Onjōji (Miidera) as a Tendai branch temple, housing the scriptures he brought back in its Tōin. In 868 he became the fifth Tendai zasu, leading the school for twenty-three years. He died in 891 at age seventy-eight and was posthumously titled "Chishō Daishi" in 927.

A versatile scholar-monk who freely synthesized Tendai and esoteric Buddhism. Despite being related to Kūkai by blood, he chose Tendai, combining passion for study in China with administrative skill in temple management.

The rivalry between Enchin's and Ennin's lineages later split Tendai into the Sanmon (Enryakuji) and Jimon (Onjōji) factions. Documents related to Enchin were inscribed on UNESCO's Memory of the World register as invaluable records of Sino-Japanese cultural exchange.