He was well known for his exploits in many battles of Ieyasu Tokugawa. In 1590, he was given a fief of 23,000 koku in Numazu (Shizuoka Prefecture) but was deprived of it when his nephew Tadachika okubo was exiled (1614). He was then made a direct Shogunate retainer with 3,000 koku. He was later offered a fief for his exploits in the battles in Osaka against the Toyotomis but declined it. Much trusted by Ieyasu, he participated in the making of important decisions of the Shogunate. Acted as a senior adviser to Shogun Hidetada and Iemitsu.
(Mikawa monogatari (Japanese Edition) [Hikozaemon Ōkubo])
Tadataka Okubo was a selfless and straightforward man, he is a famous figure in feudal romances and plays because of his eccentric actions. Okubo Seidan and Ocubo Musashi Abumi are stories telling such actions attributed to him.