 He was the fifth son of Manabe Akihiro, became "daimyō" on his uncle's death in 1814.Under Shōgun Tokugawa Ieharu he served in a variety of positions in the Tokugawa shogunate, including "Sōshaban", "Jisha-bugyō", "Osaka jōdai", "Kyoto Shoshidai" and "rōjū".In 1858, Ii Naosuke was appointed "Tairō", and Manabe was seen as his right-hand man, taking a leading role in the ratification of the Harris Treaty opening Japan to the Western powers.