In the period following the end of First World War, the Underground Electric Railways Company of London (UERL) began reviving a series of prewar plans for line extensions and improvements that had been postponed during the hostilities. Finance for the works was made possible by the government's Trade Facilities Act, 1921, which, as a means of alleviating unemployment, provided for the Treasury to underwrite the value of loans raised by companies for public works. The population of the parish of Morden, previously the most rural of the areas through which the lines passed, increased from 1,355 in 1921 to 12,618 in 1931 and 35,417 in 1951.
Unlike the other stations built for the extension, the station's platforms are not in tunnels, but in a wide cutting with the tunnel portals a short distance to the north. Three tracks run through the station to the depot, and the station has three platforms, two of which are island platforms with tracks on each side. The platforms are accessed by steps down from the ticket hall and are numbered 1 to 5 from east to west; the island platforms have different numbers for each face (2/3 and 4/5). To indicate departures, the platforms are usually referred to as 2, 3 and 5. The tunnel portals are one end of the longest tunnel on the London Underground running 27.8 kilometres (17.3 mi) to East Finchley via the Bank branch. Refurbishment and improvement works completed in 2007 included new and reconstructed cross bridges between platforms and the installation of lifts for mobility impaired passengers.
Connections: London Bus routes 80, 93, 118, 154, 157, 163, 164, 201, 293, 413, 470 and K5, and night route N155 serve the station.