Koya  was ruled by a king called a Bai or Obai. The sub-kingdoms within the state were ruled by nobles titled “Gbana”. The Koya Kingdom kept and maintained diplomatic relations with the British and French in the 18th century. Children of Temne nobles were allowed to get western educations abroad. Koya also traded with Islamic states to its north and had Muslims within its borders.

Under Nembanga’s reign (1775–1793), the Koya kingdom signed a treaty which made it possible for the establishment of a British colony on the peninsula of Sierra Leone in 1788.

Koya participated in the trans-atlantic slave trade, though sources state that such commerce was much more privatized than in other kingdoms. Subjects of Koya traded in slaves on the coast even against the wishes of the state at times.

From 1801 to 1807, Koya fought a war with British colonists and the Susu. Koya lost the northern shoreline of Sierra Leone to the British and Port Loko to the Susu. However, they remained a power in the region. In 1815, the Temne fought another war with the Susu and regained the port. In 1841, the Temne defeated the Loko tribe of Kasona on the Mabaole River dispersing many of the people. In response to a British bombardment, the kingdom expelled the Church Missionary Society missionaries operating at Magbela in 1860.