During the Edo period, the area was part of the holdings of Tosa Domain ruled by the Yamauchi clan from their seat at Kōchi Castle.

The area was organized into villages within Nagaoka District with the creation of the modern municipalities system on April 1, 1889, including Higashitoyonaga, Nishitoyonaga, Ōsugi, and Tentsubo.

Ōtoyo has a mayor-council form of government with a directly elected mayor and a unicameral town council of ten members.

Ōtoyo, together with the other municipalities of Nagaoka and Tosa Districts, contributes one member to the Kōchi Prefectural Assembly.

In terms of national politics, the town is part of Kōchi 1st district of the lower house of the Diet of Japan.