Born in 1719 into a family of low-ranking hatamoto, he served as a page to Shogun Tokugawa Ieshige, won his favour, and rose through the ranks. In 1772 he was promoted from chamberlain to senior councillor and took real control of shogunal politics (the Tanuma era). He promoted mercantilist economic policies, officially recognising and expanding merchant guilds (kabunakama), establishing the Copper and Brass offices, undertaking reclamation projects at Lake Inba and Lake Tega, and launching active development surveys of Ezo (Hokkaido). He also worked to stimulate the monetary economy and promote overseas trade. On the other hand, the prevalence of bribery in politics earned him criticism as "Bribe-Tanuma," and social anxiety mounted as the Tenmei Famine and the Asama eruption coincided. When Shogun Ieharu died in 1786 he lost power, and the following year his domains were confiscated. His innovative economic policies of the Tanuma era have recently been re-evaluated as the work of a forward-thinking politician with modern sensibilities.

A pragmatic and innovative thinker as a politician. Having overcome humble origins to rise to power, he developed flexible thinking and realistic judgment. He shifted shogunal policy away from its traditional emphasis on agriculture and promoted bold new economic policies centring on commerce and trade. The receipt of bribes was also a custom of the time, but his audacious manipulation of interests drew much criticism.

The economic policies of the Tanuma era are assessed as the first mercantilist policies in Japanese history, and some historians see in them the seeds of modern economic development. Many of his measures — the Ezo surveys and the Inba reclamation project, for example — were precursors of later Hokkaido development and agricultural land improvement. The image of "bribe politics" was also exaggerated by later generations, and his re-evaluation as an innovative politician is progressing.