The area of Inzai has been inhabited since the Japanese Paleolithic period, with some stone tools having been found in Kikaribyo that were used by people during that time.

After the Meiji Restoration, on April 1, 1889, the town of Kioroshi, and the villages of Omori, Taisha, Funoho, Rokugo, Munakata, Hongo and Eiji were founded with the establishment of the modern municipalities system.

Inzai has a mayor-council form of government with a directly elected mayor and a unicameral city council of 22 members.

In terms of national politics, the city is part of Chiba 13th district of the lower house of the Diet of Japan.

Its location and good transportation connections between Tokyo and Narita International Airport have led to numerous logistics companies establishing warehouse and distribution centers in the city.

The development of Chiba New Town has also greatly increased the number of commuter residents, with over 24% of the working population traveling to Tokyo daily.