The station opened as Northfields Halt on 16 April 1908, renamed Northfields and Little Ealing in 1911 and finally named Northfields in the 1930s.

Northfields is only on one line, but has two westbound and two eastbound tracks because of a depot just beyond the station where trains often terminate. One eastbound track carries trains that have just come from the depot, and the other takes trains that have come from stations further west. Similarly, one of the westbound tracks is for terminating trains, and the other for trains going on to Heathrow.

Pre-1900 maps of Ealing show Northfields as almost entirely rural, with a few houses and orchards. The arrival of the Metropolitan District Railway in 1883 prompted development of the area.