The route is U-shaped, running from Ogikubo Station in the west of the city via the commercial and administrative district of Shinjuku through to the Marunouchi commercial center around Tokyo Station, before turning back and heading to Ikebukuro.

In response to crowding, Tokyo Metro upgraded all stations with chest-high platform doors on March 28, 2009, a date on which it also began driver-only operation.

A 1.2 km (0.75 mi) segment between Akasaka-mitsuke and Yotsuya began construction in 1942, but was abandoned in 1944 as a result of the continuing effects of World War II.

On December 7, 1946, the Marunouchi Line was revised to begin from Nakano-fujimichō to the Mukōhara neighbourhood in Toshima Ward via Kanda and Ikebukuro, for a total length of 22.1 km (13.7 mi).

On March 30, 1951, a groundbreaking ceremony was held at Ikebukuro Station East Exit to begin construction of the initial 7.7 km (4.8 mi) segment of the Marunouchi Line.

A plan to extend the Marunouchi Line from Ogikubo to Asaka City in Saitama Prefecture was rejected in the late 1990s.

The line, stations, rolling stock, and related facilities were inherited by Tokyo Metro after the privatization of the Teito Rapid Transit Authority (TRTA) in 2004.