The area of Northwood consists of the elevated settlement of Northwood and Northwood Hills, both of which are served by stations on the Metropolitan Line.

A 1565 survey of Northwood conducted by King’s College, Cambridge - new lords of the manor of Ruislip - recorded ten houses and several farms.

David Carnegie owned the large Eastbury Park Estate in the north of the area in 1881. In 1887, the Metropolitan Railway was extended from Harrow-on-the-Hill to Rickmansworth and Carnegie sold his land to developer Frank Carew. After some building, Carew sold the majority of the estate to George Wieland in 1892. The High Street had been hitherto a track leading on from Rickmansworth Road to Gate Hill Farm. The first shops there opened in 1895.

Northwood and Pinner Cottage Hospital was built in 1926.

Northwood is home to the British Armed Forces Permanent Joint Headquarters (PJHQ) for planning and controlling overseas military operations, together with the NATO Maritime Command.

Northwood was used for location filming of the houses and surrounding streets in the BBC TV sitcom The Good Life, pretending to be Surbiton.