Kōzaki was historically part of Shimōsa Province until the formation of Chiba Prefecture at the beginning of the Meiji Period (1868 – 1912).

Kōzaki and Yonezawa villages were founded on April 1, 1889 within Katori District of Chiba Prefecture with the creation the modern municipalities system.

[1] Kōzaki has a mayor-council form of government with a directly elected mayor and a unicameral town council of 13 members.

Kōzaki, together with the city of Katori and town of Tako, contributes two members to the Chiba Prefectural Assembly.

In terms of national politics, the town is part of Chiba 10th district of the lower house of the Diet of Japan.