The cause of his death was said to be illness, but there are theories that say he fainted when he heard the news of the dismissal of Yoritsugu and died, as well as stories which say that Michiie was assassinated by the bakufu since he secretly possessed had a strong influence.
なお、彼の死因は病死と言われているが、頼嗣失脚の報を聞いてそのまま卒倒して死去したとする説や、隠然たる影響力を持つ道家の存在を苦々しく思った幕府によって殺されたとする暗殺説もある。