Mizunami's biggest claim to fame came in 1995, when the largest ceramic plate in the world, as recognised by the Guinness Book of Records, was created by the Inatsu Town Planning Association in the city.

During the Edo period, the area was tenryō territory under direct control of the Tokugawa shogunate.

The Nakasendō highway connecting Edo with Kyoto passed through the area, and Ōkute-juku and Hosokute-juku were located within what are now the city limits.

The modern city was founded on April 1, 1954 by the merger of Mizunami-Toki Town with the villages of Kamado, Okute, and Hiyoshi.

Mizunami has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 16 members.