It is served by the 1 Line, part of Sound Transit's Link light rail system, and also connected above ground by buses at several stops, the South Lake Union Streetcar, and the Seattle Center Monorail.

Westlake station consists of two underground side platforms, connected to the surface by entrances and a mezzanine level served by nearby department stores.

[2] The station is at the north end of Downtown Seattle, near the Denny Triangle area, and is within walking distance of the Pike Place Market Historic District.

According to the Puget Sound Regional Council, the area within 1⁄2 mile (0.8 km) of the station has an estimated population of 15,171 people (in 12,995 total housing units, mostly in multifamily buildings) and approximately 91,055 jobs.

[7] The newly regraded area was part of urban planner Virgil Bogue's 1911 comprehensive plan for Seattle, envisioning a civic center to the north and several subway lines converging at the intersection of Pine Street and 3rd Avenue.

The subway lines would continue outwards to serve the civic center, Capitol Hill, Downtown (modern-day Pioneer Square), and the waterfront; the stations would also include additional entrances from within department stores and other large buildings.

[10][11] The regraded area was developed into the city's retailing neighborhood in the 1920s, with the construction of large department stores for The Bon Marché, Frederick & Nelson, and Nordstrom on Pine Street between 3rd and 6th avenues.

It called for a subway station on 3rd Avenue between Pine and Pike streets, designed with underground connections to major stores, would be served by two routes continuing north to Ballard (via Lower Queen Anne) and Lake City (via Capitol Hill and the University District).

[25] SCI Contractors of Calgary was awarded the $74.5 million contract for the Pine Street segment, including the construction of Westlake and Convention Place stations, in February 1987.

[27] Pine Street was briefly re-opened for the Christmas shopping season, from November 2 to January 4, at the request of downtown merchants; the excavated tunnel was backfilled and given a temporary surface for automobile traffic.

[33][34] Excavation and concrete pouring in Westlake station were completed in December 1988, leaving major work on the mezzanine level left to finish.

[41] The mezzanine remained open for several weeks, allowing for access between the basement levels of downtown retailers, but closed until November for additional construction.

[47][48] In the early 1990s, a regional transit authority (RTA) was formed to plan and construct a light rail system for the Seattle area.

[52][53] Ownership of the tunnel, including its stations, was transferred to Sound Transit in 2000 but returned two years later to King County Metro under a joint-operations agreement.

The two-year renovation included the installation of new rails, a lowered roadbed at stations for level boarding, new signalling systems and emergency ventilation.

Contractors working on an existing clock foundation drilled 48 inches (120 cm) through the station roof and broke part of a structural girder over the northbound tracks.

[70][71] Sound Transit later adjusted the temporary schedule to use alternating trains every 15 to 20 minutes that required a single transfer at Pioneer Square station due to a lack of shuttle buses.

[82][83] The mezzanine also has ticket vending machines that issue ORCA cards, and was formerly home to the King County Metro Customer Shop, which was located at the west end of the station.

[85][86] The station's stairways and surface entrances are inscribed with quotes from University of Washington professor Caroline Ober, artist Mark Tobey, and retailer Silas Munro.

[70] The platform level houses three 35-foot-long (11 m), 10-foot-tall (3 m) porcelain enamel murals by Seattle artists Fay Jones, Gene Gentry McMahon, and Roger Shimomura.

It was created in 2009 by Christian French as part of the Stellar Connections series and its points represent nearby destinations, including Pike Place Market, Victor Steinbrueck Park, the Paramount Theatre, and the Washington State Convention Center.

[96] Bus stops on Pine and Pike streets serve local routes headed east to Capitol Hill, Montlake, and Madison Park.