The west side of the city area is almost flat with an average elevation of only ten meters above sea level.

The monk Dōkyō, who was from Yuge clan, became the most powerful person in the late Nara period through his relationship with Empress Shōtoku.

He constructed Saikyo (West Capital) called Yuge-gu in this area, from which he intended rule the nation prior to his fall from power.

During the Nara period, the area Yao prospered as a transportation hub between Yamato Province, Naniwa-kyō and the seacoast.

During the Heian period, the area was dominated by large shōen landed estates controlled by Buddhist temples and the nobility.

However, due to flooding, the Tokugawa shogunate undertook a large public works project to change the flow of the Yamato River from east to west, to empty into Osaka Bay directly.

Yao has a mayor-council form of government with a directly elected mayor and a unicameral city council of 28 members.

In terms of national politics, the city is part of Osaka 14th district of the lower house of the Diet of Japan.