In the Edo period, the Mori clan, who were the first daimyō of Tsuyama Domain, gave local merchants the same level of authority as merchants in the castle town of Tsuyama, making it the center of eastern Mimasaka.

Mimasaka has a mayor-council form of government with a directly elected mayor and a unicameral city council of 18 members.

Mimasaka, collectively with the village of Nishiawakura, contributes one member to the Okayama Prefectural Assembly.

In terms of national politics, the city is part of the Okayama 3rd district of the lower house of the Diet of Japan.

Mimasaka has a mixed economy based on manufacturing, wholesale and retail commerce, agriculture, forestry, and tourism (hot springs).