Saiwai Ward is located in eastern Kanagawa Prefecture, in the center portion of the city of Kawasaki, bordering on Tokyo to the north and Yokohama to the south.

After the Meiji Restoration, the area urbanized due to its proximity to Kawasaki Station on the Tokaido Main Line.

Saiwai Village within Tachibana District in the new Kanagawa Prefecture was created on April 1, 1889 through the merger of eight smaller hamlets.

In the early twentieth century, the area was dominated by factories; notably Meiji Sugar and Toshiba.

The economy of Saiwai Ward continues to be dominated by industry, with Toshiba, Canon, Pioneer Corporation, and Hitachi.