The line runs between Nakano in Nakano-ku, Tokyo and Nishi-Funabashi in Funabashi, Chiba Prefecture.

[1] On maps, diagrams and signboards, the Tōzai Line is shown using the color "sky blue" and its stations are given numbers using the letter "T".

The line runs through central Tokyo from east to west via Takadanobaba, Waseda, Ōtemachi, Nihombashi, Kiba and Urayasu.

Through services to Mitaka via the JR East Chūō Line and Tōyō-Katsutadai via the Tōyō Rapid Railway run all day.

During the morning and evening peak periods, through services run to Tsudanuma via the JR East Sōbu Line.

^ Crowding levels defined by the Ministry of Land, Infrastructure, Transport and Tourism:[7][8]