Like all stations on the Cockfosters extension, Turnpike Lane station set new aesthetic standards, not previously seen on London's Underground. During the planning period of the extension to Cockfosters, alternate names for this station (North Harringay and Ducketts Green (Ducketts Common is located opposite)) were considered but rejected.
Architecturally, this tube station, designed by the architect Charles Holden, is a well-preserved example of the modernist house style of London Transport in the 1930s. The station ticket-hall is an enormous brick box, with two large ventilation towers, half-sunk into the surrounding ground. Its high walls contain segmented windows which during the day allow natural light to shine far into the station. The effect in late afternoon light is akin to that in a cathedral transept. Two of the street level entrances gave access to the tram routes to and from Alexandra Palace via tramway island exits into Turnpike Lane. These tram services were withdrawn in 1938 and replaced by buses which continued to use the tram islands until 1968 when they were removed.
The sub-surface areas of the station are tiled in biscuit coloured tiles lined with yellow friezes. The station tunnels have, in common with those of Manor House and Wood Green, a diameter of 23 feet (7 metres) and were designed for the greater volume of traffic expected. In contrast, Bounds Green and Southgate have only 21 foot (6.4 metres) diameter platform tunnels. The construction of "suicide pits" between the rails was also innovative. These were built in connection with a system of passageways under the platforms to give access to the track.
The bus station at the back of the station complex was covered in 1968 as part of a "reshaping plan" of London bus services. The roof has since been removed as part of the rebuilding in the late 1990s.