The underground station is served by the Bakerloo line. It is between Baker Street and Edgware Road stations and is in Travelcard Zone 1. Access is via a set of escalators from the mainline station concourse, which also houses the underground station's ticket office.
Compared to some of the other London termini, the mainline station's Underground links are poor. This is because the mainline station was opened thirty-six years after the Metropolitan Railway constructed the first part of what is now the northern section of the Circle line which bypasses the station to the south.
For mainline passengers wishing to use services on the Circle, Jubilee, Hammersmith and City or Metropolitan Lines, it may often be quicker to walk the short distance to nearby Baker Street station, than to make the journey on the Bakerloo line and change trains there.
The underground station is accessed through a separate set of ticket barriers to the main line platforms. Until 2004 a wooden escalator led downwards into the station, one of the last left on the London Underground that had yet to be replaced with a newer metal equivalent.
The underground station was opened on 27 March 1907 by the Baker Street and Waterloo Railway under the name Great Central (following a change from the originally-intended name Lisson Grove), and was renamed Marylebone on 15 April 1917. The original name still appears in places on the platform wall tiling, although the tiling scheme is a replacement designed to reflect the original scheme.
The present entrance opened in 1943 following the introduction of the escalators and wartime damage to the original station building that stood to the west, at the junction of Harewood Avenue and Harewood Row. This building, designed by the Underground Electric Railways Company of London's architect, Leslie Green, had used lifts to access the platforms. It was demolished in 1971 and the site is now occupied by a budget hotel.
London Buses Routes 2, 13, 18, 27, 30, 74, 82, 113, 139, 189, 205, 274, 453 and Night Routes N13, N18, N74 and N111, N205 serve the station.