Ii Naoyoshi served as a bushō during the Sengoku period.  He was a retainer of the Imagawa clan.

Naoyoshi was born as the fourth son of Ii Naohira, the lord of IInoya Castle in the Inasa District of Tōtōmi Province.

The Ii were kokujin, or provincial landowners, in Tōtōmi.  Naoyoshi, together with his father, served Imagawa Yoshimoto.  Ii Naomori (Naoyoshi’s nephew and the lineal heir of Naoyoshi’s eldest brother, Ii Naomune) did not have a son so Ii Naomitsu (Naoyoshi’s second oldest brother) promised to send his own son, Kamenosuke (later known as Ii Naochika), as an adopted heir of Naomori.  This, however, invited opposition from retainers of the Ii clan who were against the succession by Naochika to the headship of the clan.  In particular, Naomitsu did not for some time get along well with Ono Masanao, a chief retainer of the Ii family.

In 1541, the Ii were subordinate to the Imagawa clan who served as the lords of Suruga Province.  The Kai-Takeda clan began to encroach on the territory of the Ii in Tōtōmi so, within the Ii family, Naohira had Naomitsu and Naoyoshi conduct military preparations.  Masanao then slandered them by telling Imagawa Yoshimoto that Naomitsu and Naoyoshi were traitorous.  On 12/23 of Tenbun 13 (1544), Naomitsu and Naoyoshi were summoned to Sunpu to explain themselves to Yoshimoto but were murdered instead.  After returning from Sunpu to Iinoya, Masanao, following orders of Yoshimoto, attempted to kill Kamenosuke (Naochika) but, with the assistance of his chief retainer, Imamura Masazane, he fled to Shinano Province.