Even after Ieyasu became subordinate to the Toyotomi Clan, Tadatsugu was favorably treated by Hideyoshi TOYOTOMI as the number-one chief vassal of Ieyasu, and in 1586, he was granted the rank of and appointed to the office of Jushiinoge (junior fourth rank, lower grade) Saemon no jo, which was the highest rank in the family.
家康が豊臣氏の傘下に入ったのちも、豊臣秀吉から家康第一の重臣として遇され、天正14年（1586年）には家中では最高位の従四位下・左衛門督に叙位・任官された。