[7] In 1858, Nakayama was a leader of courtiers protesting against the Treaty of Amity and Commerce between Japan and the United States, which opened the ports of Kanagawa, Kobe, Nagasaki, Niigata, and Hakodate to foreign trade and also to settlement by Americans.

However, this banishment was ended in January 1867 when Kōmei died unexpectedly and Nakayama's grandson, a boy aged only fourteen, came to the imperial throne.

[4] On 3 January 1868, when Iwakura Tomomi arranged the seizure of the Kyoto Imperial Palace and initiated the Meiji Restoration, which resulted in the creation of the post-Shōgun Empire of Japan, Nakayama was among the courtiers who supported this action.

On 14 May 1888, a month before his death, he received the supreme accolade of being awarded the Grand Cordon of the Order of the Chrysanthemum during his lifetime,[2] a rarely bestowed honour.

His eldest son Tadanaru would die before him, so Nakayama's grandson Takamaro would succeed Tadayasu as the 2nd Marquess, serving as court adviser and chamberlain (東宮侍従) to his cousin, the crown prince Taishō.