It originates at Ikebukuro Station, a large railway junction in north-western Tokyo, extending to northwest suburbs as far as Tokorozawa, Saitama, and nominally terminates at Agano Station.

The Seibu Chichibu Line from Agano to Seibu-Chichibu Station is an extension.

There is also a passing loop inside a tunnel where the signal controls bi-directional operation.

[citation needed] In 2001, a second track of 350 m was built to complete the double-track section from Ikebukuro to Hannō.

[citation needed] Station numbering was introduced on all Seibu Railway lines during fiscal 2012, with Seibu Ikebukuro Line stations numbered prefixed with the letters "SI".