Baker Street station was opened by the Metropolitan Railway on 10 January 1863 - these platforms are now served by the Circle and Hammersmith & City lines. On 13 April 1868, the Met opened the first section of Metropolitan and St John’s Wood Railway as a branch from its existing route. This line, serving the open-air platforms, was steadily extended to Willesden Green and northwards, finally reaching Aylesbury Town and Verney Junction (some 50 miles from Baker Street) in 1892.

Over the next few decades this section of the station was extensively rebuilt to provide four platforms. The current Metropolitan line layout largely dates from 1925, and the bulk of the surface buildings, designed by architect Charles Clark, also date from this period.

The Baker Street & Waterloo Railway (now the Bakerloo line) opened on 10 March 1906; Baker Street was the temporary northern terminus of the line until it was extended to Marylebone station on 27 March 1907.

The original station building stood on Baker Street and served the tube platforms with lifts, but these were supplemented with escalators in 1914, linking the Metropolitan line and the Bakerloo line platforms by a new concourse excavated under the Metropolitan line.

On 20 November 1939, following the construction of an additional southbound platform and connecting tube tunnels between Baker Street and Finchley Road stations, the Bakerloo line took over the Metropolitan line’s stopping services between Finchley Road and Wembley Park and its Stanmore branch. The current Bakerloo ticket hall and escalators to the lower concourse were provided in conjunction with the new service.

The Jubilee line added an extra northbound platform and replaced the Bakerloo line service to Stanmore from its opening on 1 May 1979.