Ihara Tadatane served as a bushō during the Sengoku period. He was a retainer of the Imagawa clan and served as the lord of Ihara Castle in Suruga Province.
Tadatane originated from the Yui clan and was adopted by Ihara Tadamoto. Later, he inherited the headship of the Ihara clan.
In 1541, Takeda Nobutora, a sengoku daimyō, was ousted from Kai Province by his son, Takeda Harunobu (Shingen), who took over the Kai-Takeda clan. As a result, Nobutora fled for safety to the Imagawa family in neighboring Suruga. At the time, Suruga was under the control of Imagawa Yoshimoto.
In 1560, Yoshimoto died in a lightening assault by the forces of Oda Nobunaga at the Battle of Okehazama. In this battle, many members of the Ihara family were lost along with Imagawa forces. Yoshimoto was succeeded by his lineal heir, Imagawa Ujizane. 1561, Tadatane purportedly impeded a plot by Nobutora to launch a revolt against Ujizane, and succeeded in expelling Nobutora from Suruga. In 1569, after Takeda Shingen invaded Suruga, Tadatane served in the vanguard forces to resist the Takeda army at Yui but was defeated at the Battle of Sattatōge.
Taigen Sessai, a close associate of Imagawa Yoshimoto, was the uncle of Tadatane’s wife.