Following the establishment of the Kamakura shogunate in 1185, members of the clan were granted the post of Constable (Shugo) of Bungo and Buzen Provinces in Kyūshū.
As the Ōtomo were one of the major clans of Kyūshū, along with the Shōni and the Shimazu, they had a central role in organizing efforts against the Mongol invasions of Japan in 1274 and 1281. They also played an important role in the establishment of the Ashikaga shogunate, in the 1330s. Ōtomo warriors fought alongside those of Ashikaga Takauji and enabled him to win a number of key battles, including the battle of Sanoyama; this helped to ensure them powerful government positions in the new shogunate. A powerful clan throughout the Sengoku period (1467–1573), the Ōtomo are especially notable as one of the first clans to make contact with Europeans, and to establish a trade relationship with them. In or around 1542, three Portuguese ships were carried by a typhoon to the island of Tanegashima, just off the coast of Kyūshū. Within ten years, trade with the Portuguese was fairly regular and common in Kyūshū. The Jesuit missionary Francis Xavier arrived in Japan in 1549, and soon afterwards met with Ōtomo Sōrin, shugo of Bungo and Buzen provinces, who would later be described by Xavier as a "king" and convert to Roman Catholicism in 1578. Ōtomo was eager to secure for his clan further trade and contact with the Portuguese, seeing the technological and, more importantly perhaps, economic benefits that could be derived. In 1552, emissaries from the Ōtomo clan traveled to Goa with Xavier, to meet with the Portuguese Governor of India. Xavier and other Jesuit missionaries would return to Kyūshū, traveling and proselytizing; the Ōtomo were always well-disposed towards them, and they saw some success in Bungo as a result, converting many Japanese to Christianity.
Towards the end of the 16th century, the Ōtomo fought both the Shimazu and Mōri clans, of whom the latter were expert sailors. Though they did not play a major role in the campaigns of Tokugawa Ieyasu which ended the Sengoku period, they did retain their domains into the Edo period.
Its members include:
- Ōtomo no Kuronushi – classical poet
- Ōtomo Sōrin (1530–1587), Constable of Bungo and Buzen Provinces
- Sansom, George (1961). "A History of Japan: 1334–1615." Stanford, California: Stanford University Press.
- Turnbull, Stephen (1998). 'The Samurai Sourcebook'. London: Cassell & Co.