After having been placed under his nephew Kiyomori's charge, he was easily executed together with his four sons without plea for sparing his life (Kiyomori reportedly forced Tadamasa to change his name to Tadasada because he had the same name as FUJIWARA no Tadamasa).
そして甥の清盛に預けられるが、さしたる助命嘆願もなく親子五人並んであっさりと処刑されてしまった（なおこの際、名前の読みが藤原忠雅と同じであることを憚り、「忠貞」と改名させられたという）。