He served as the guardian (Shogun Kokenshoku) of the 14th Shogun Iemochi TOKUGAWA; after Iemochi's death he assumed his position as the 15th Shogun of the Edo Shogunate.
将軍後見職として後見を務めていた14代将軍徳川家茂の死去後、江戸幕府第15代将軍に就任。