Yoshinao Tokugawa was fond of learning, and versed in Confucianism and Shintoism.
While still a young child, he was appointed leader of first the fief of Kofu in Kai Province and later the fief of Kiyosu in Owari Province. In 1610, he was appointed leader of the Owari Domain (present-day Nagoya), one of the most important regions in the country, thus founding the Owari-Tokugawa house. A holder of the 2nd court rank, junior grade (ju-ni-i), he had the title of dainagon (major counselor).
During the Kan'ei era (1624-1644) he had a kiln constructed at the corner of the Ofuke enceinte (Ofukemaru) of Nagoya Castle and invited potters from Seto to make pottery there. This became to be known Ofukei ware.
Yoshinao began learning Shinkage-ryū from Yagyū Hyōgonosuke at age 16, and was named the 4th sōke at age 21.
His remains were cremated and laid to rest at his mausoleum in Jōkō-ji (Seto).
Yoshinao's principal wife was Haruhime, the daughter of Asano Yoshinaga of Kii (whose family was later transferred to Hiroshima), and his concubines included Osai and Ojō no Kata. He had two children: Mitsutomo, who succeeded him as daimyō of Owari, and Itoko or Kyohime who married Hirohata Tadayuki, a court noble.