Gamō Satoyoshi served as a bushō during the Sengoku and Azuchi-Momoyama periods.
Initially, Satoyoshi was adopted by Uesaka Hyōgo-no-suke, a dogō, or powerful local clan, in Ōmi Province. He adopted the name of Uesaka Sabun and became a retainer of Azai Nagamasa (the sengoku daimyō of northern Ōmi). After the demise of his lord in 1573, he then served Shibata Katsuie.
In 1583, following a defeat at the Battle of Shizugatake, Katsuie killed himself at Kita-no-shō Castle in Echizen and the Shibata family lost their influence. After wandering without a lord, Sabun requested to serve under Hashiba Hideyoshi relying upon Gamō Ujisato from Ōmi to persuade him, but Ujisato was impressed by his bravery and, instead, had him serve the Gamō family. In 1587, Satoyoshi served in the vanguard of an attack on Ganjaku Castle during the Subjugation of Kyūshū by Hideyoshi, after which he was recognized for his contributions on the battlefield. He was then permitted to adopt the Gamō surname and became Gamō Satoyoshi. During the Conquest of Odawara by the Toyotomi, the Gamō forces deployed on the side of the Toyotomi, but, in an attack on Nirayama Castle defended by the Odawara-Hōjō clan, he fought valiantly despite being shot by an arquebus. Thereafter, during the Siege of Odawara Castle by the Toyotomi army, Ōta Ujifusa (fighting for the Hōjō) launched a nighttime attack against the base of the Gamō but was vigorously repelled by Satoyoshi and his fellow soldiers
In 1590, after the Gamō family was reassigned to Aizu in Mutsu Province, Satoyoshi moved into the mountain fortress known as Hisakawa Castle with a fief of 10,000 koku. Together with Gamō Satonari, Satoyoshi invited Sakuma Yasumasa and Sakuma Katsuyuki (two brothers and masterless samurai whom they knew from their time under the Shibata family) to serve as yoriki, or security forces. During the Kasai-Ōsaki Uprising, Satoyoshi remained behind to protect the castle and supplied gunpowder to Ujisato who was holed-up in Myō Castle. In In 1591, Kunohe Masazane, a powerful figure in the Nanbu clan, revolted against Nanbu Nobunao (the head of the clan) and the Oushū Retribution by the Toyotomi army in an event known as the Revolt of Kunohe Masazane. During this event, Satoyoshi attacked Nukabe Castle. After the conflict, he became the lord of Nakayama Castle with a fief of 13,000 koku.
In an internal conflict known as the Gamō Disturbance which ran from 1595 to 1598 during the deployment to the Korean Peninsula (the Bunroku-Keichō Campaign), Satoyoshi came into conflict with Gamō Satoyasu, the head of the magistrates serving the Toyotomi administration during the Oushū Retribution. This was finally resolved trough the mediation of Gamō Satonari. After the death of Ujisato, in 1598, during the era that Gamō Hideyuki governed the territory in Aizu, Satoyoshi ousted Satoyasu for the murder of Watari Yoshiaki. In the third month of 1598, Hideyoshi ordered Hideyuki to transfer from Aizu with a fief of 92,000 koku to Utsunomiya in Shimotsuke Province with a fief of 18,000 koku whereupon Satoyoshi became the lord of Kawahara Castle with a fief of 6,000 koku, but died shortly thereafter.