Miyahara Kagetane served as a bushō during the Sengoku and Azuchi-Momoyama periods.  He was a retainer of the Shimazu clan.

His ancestor was one of nine individuals serving as a yoriki, or security officer, for Shimazu Tomohisa, the illegitimate eldest son of Shimazu Tadakuni.

Kagetane served Shimazu Takahisa and, in 1567, participated in an attack against the Hishikari clan.  The next year, during attacks by the allied forces of the Hishikari and Sagara clans, Kagetane entered Sogi Castle.  With additional forces from Sata Hisamasa, Kagetane defended the castle against an assault by the Hishikari, the Sagara, and the Shibuya.  In the following year, Kagetane joined an attack by Niiro Tadamoto against Ōkuchi Castle (held by the Hishikari).  Together with Ōno Tadamune, he made contributions in an ambush on Mount Inari in Hatsuki-Togamio.

In 1576, Kagetane contributed to the capture of Takahara Castle and, thereafter, was appointed as the steward of Suki.  Kagetane served at the Battle of Mimikawa in 1578 and, in 1581, in the invasion of the Ashikita District in Higo Province.  In 1583, he was also appointed as the steward of Sashiki in Higo.

In the fourth month of 1587, during the Subjugation of Kyūshū by Toyotomi Hideyoshi, Kagetane was killed in action when attacked by members of the kokujin group at Kuma-no-shō in Higo.