Tadamasa Taira was born in Japan. He was the second son of Masamori and uncle of Kiyomori.
In the war of Hogen Era (1156), he defended the Shirakawa Palace at the command of ex-Emperor Sutoku. Defeated, he became a Buddhist priest and surrendered. Although Tadamasa asked for Kiyomori's intercession, Kiyomori refused it and was condemned to death. He and four members of his family were executed in Kyoto.