Paddington is served by four London Underground lines through two separate stations: the Bakerloo, Circle and District lines have a combined sub-surface and deep-level station to the south of the main line station, and the Hammersmith & City and Circle lines have a sub-surface station to the north. Circle line services go through both of the sub-surface stations as part of a spiral route. Although shown on the London Underground map as a single station, the two sub-surface parts are not directly linked.
Although Paddington is not served by the Central line, the short walk to Lancaster Gate tube station is taken by many commuters heading for the West End or the City, as it can be quicker than alternative routes.
The first underground railway station was opened as Paddington (Bishop's Road) by the Metropolitan Railway (MR) on 10 January 1863 as the terminus of the line from Farringdon. The station was to the north of the main line station and, from 13 June 1864, MR services were extended westward via a connection to the GWR's Hammersmith branch, now the Hammersmith & City line.
On 1 October 1868, the MR opened a branch to Gloucester Road, with a station called Paddington (Praed Street) in a cut-and-cover tunnel parallel to that street south of the mainline station. The deep-level Baker Street and Waterloo Railway (now the Bakerloo line) station opened on 1 December 1913 as a temporary terminus of an extension from Edgware Road to Queen's Park.
Services on what became the Circle line in 1949 were originally shared by the MR and the District Railway. Hammersmith & City line services were originally operated as part of the MR (later the Metropolitan line) and were separately identified as the Hammersmith & City line in 1990.
From December 2009, the Circle line was altered so that trains run in a spiral from Hammersmith via Ladbroke Grove to the Bishops Road platforms at Paddington, then on to Edgware Road, Kings Cross, Tower Hill, Victoria, High Street Kensington and back to Edgware Road via the Praed Street platforms at Paddington. This means that eastbound trains from the District and Circle line platforms all terminate at Edgware Road, the next station. Passengers for stations beyond Edgware Road either have to change there, or use services from the Hammersmith & City line platforms. All trains towards King's Cross now leave from the same platform, instead of being split between two platforms some distance apart.
The platforms of the Hammersmith & City and Circle lines (Bishop's Road) station are still separate from the other Underground platforms; they are numbered (15 and 16) in the same sequence as the mainline platforms. Interchange between the Bakerloo, District and Circle line platforms and the Hammersmith & City and Circle line platforms involves walking the length of the mainline station outside the Underground barrier lines, although the ticket barriers are programmed to permit changing between the two stations as part of a single journey.
Hammersmith & City line trains run between Hammersmith and Barking via Paddington (Suburban) platforms 15 and 16. Circle line trains share tracks with the Hammersmith & City line from Hammersmith to Liverpool Street, then around a clockwise loop via Aldgate and Victoria, arriving back at Paddington (Praed Street), before terminating at Edgware Road. District line services run between Wimbledon and Edgware Road, and Bakerloo line trains run between Elephant & Castle and Harrow & Wealdstone stations.
London Buses routes 7; 23; 27; 36; 46; 205; 332; 436 and night route N7 and N205 serve the station.