It extends 82.5 km (51.3 mi) from Shinjuku in central Tokyo through the southwest suburbs to the city of Odawara, the gateway to Hakone in Kanagawa Prefecture.

It is a busy commuter line and is also known for its "Romancecar" limited express services.

Notes: Legend: [2] The Odawara Express Railway Co. opened the entire line on 1 April 1927 in order to allow for the Emperor's family to travel on the line, though as duplication works were not completed until October that year, there was initial timetable and signalling issues.

[3] Increasing traffic volume since the 1970s led to plans being formed in 1985 for a track upgrading project on the Odawara Line, though land acquisition issues stalled major track expansion work until construction began in 2013;[4] the project is being carried out between Yoyogi-Uehara and Mukōgaoka-Yūen, quadrupling the Odawara Line trackage and stacking the tracks underground, allowing for increased express services.

[5] Originally a viaduct was planned but this was changed to underground tracks, and work on the tunnel between Setagaya-Daita and Higashi-Kitazawa was completed in 2018.