The station was opened by the London and Birmingham Railway (L&BR) as Harrow on 20 July 1837 in what was then rural Middlesex. At the time the station was built, the area was fields and the nearest large settlement was at Harrow on the Hill about 1.5 miles (2.4 km) to the south. Wealdstone was a collection of houses at the north end of what is now Wealdstone High Street, about 1 mile (1.6 km) north of the station. The station buildings on the south west (Harrow) side of the station are the older part of the station, located beside what were the fast lines until the platforms were used for the later Euston to Watford DC line and the main line tracks were re-routed through the previous slow line platforms and new platforms (numbers 5 and 6) to the north east; a new, larger, station building was also erected on this Wealdstone side of the station in 1912. The station footbridge was originally constructed with a full-height central barrier with passengers using the "London" side and railway and postal staff using the "country" side to move goods and mail via lifts which were removed in the early 1970s, leaving two parcel elevators serving the DC line platforms for the remaining postal traffic.

On 18 December 1890, a short branch line known as the Stanmore branch line was opened by the London & North Western Railway (LNWR, successor to the L&BR). It ran 2.12 miles (3.41 km) north-east from the main line to Stanmore. In 1932 an intermediate halt was constructed as Belmont to serve the developing residential areas locally. The train was known affectionately as the "Belmont Rattler".

By the end of the 19th century Wealdstone had developed in size and the station was given its current name on 1 May 1897 to reflect more accurately its location.

On 16 April 1917, Bakerloo line services were extended from Willesden Junction to Watford Junction running on the newly electrified local tracks (the New Lines, which were originally steam-worked) and calling at Harrow & Wealdstone from that date.

On 15 September 1952, the passenger service to Stanmore – by then renamed Stanmore Village to avoid confusion with the Metropolitan Railway's (later Bakerloo, and now Jubilee) station opened in 1934 – was withdrawn. Freight traffic (particularly the storage of bananas) continued sporadically until 1964.

During the early 1960s, as part of the West Coast Main Line electrification, the bridge carrying the A409 road (The Bridge/Station Approach) over the railway was rebuilt easing the previous severe road gradients and offering higher clearance over the tracks to allow for overhead catenary cabling.

On 5 October 1964, all services on the branch line to Belmont were withdrawn as part of the cuts of the Beeching Axe. The permanent way north of Harrow and Wealdstone station was removed but the disused platform 7 on the eastern side of the station was left in place as a siding for a further few years until it too was removed.

On 24 September 1982, Bakerloo line services to Harrow & Wealdstone ended when services north of Stonebridge Park were ended. However the closure was short-lived, and the Bakerloo line to Harrow & Wealdstone was reinstated on 4 June 1984 with the station acting as the terminus.

In the 1990s major reconstruction of local roads made to by-pass High Street, Wealdstone sent a new road (Ellen Webb Drive) through what remained of the station goods yard and part of the forecourt of the eastern entrance (1917) to the station.

• On 7 August 1838 Thomas Port was fatally injured when he fell from a train and was run over about 1+1⁄4 miles (2 km) south of the station.
• In 1870, a mail train was in a rear-end collision with a freight train. Eight people were killed, including the cricketer James Rowley.
• Harrow and Wealdstone rail crash: On 8 October 1952, the station was the site of the worst peacetime railway disaster in British history when 112 people were killed and 340 were injured as a result of a Scottish express train colliding with the rear of a local train standing at platform 4. Seconds later a northbound express hauled by two locomotives collided with the wreckage causing further injury and demolished one span of the footbridge and the northern end of platforms 2 and 3. A memorial plaque was placed above the main entrance on the eastern side of the station to mark the 50th anniversary in 2002.

The station has undergone several improvements in recent years: removal of the central barrier to allow use of the full width of the footbridge (which links both entrances and all platforms); new lifts for the use of disabled persons; newly painted and brightly-illuminated waiting rooms. When the line was resignalled with standard BR signalling in the 1980s, the two reversing sidings (used for turning Bakerloo line trains and occasionally DC line trains) located between the tracks of the DC line at the northern end side of the station were replaced by a single siding. This allowed the curve at the northern end of platform 2 to be eased using the space vacated by the removed siding. In practice, the remaining siding became unavailable for use by LO trains except when Bakerloo trains are not running as current (2018) service levels means that the siding is not sufficient for the reversing of Bakerloo trains, some trains have to reverse in platform 1 as well. Harrow and Wealdstone (together with Willesden Junction) is one of the two stations on the DC line which can be used for turning or stabling trains clear of the running lines during reduced or disrupted services although trains can be reversed using crossovers at other stations.

Ticket gatelines have been installed at both entrances in addition to the pre-existing booking offices

Trains on the fast lines pass the station through platforms 3 & 4, usually without stopping to serve it; access to these platforms is now by staff-operated gates which are opened when necessary. Southern and London Northwestern Railway stopping services generally use platforms 5 & 6 on the slow lines but all can use either pair of platforms when needed since the four main line platforms were lengthened to take 12-coach trains. Platform 2 on the Up DC line has unusually been maintained at a length of 182m rather than the usual DC line length of around 125m, long enough for an 8-coach train; on rare past occasions in recent years involving total closure of the fast and slow lines, main line trains have been diverted over the DC line between Watford Junction and Euston but without stopping at intermediate stations.

v t e London Overground
Cheshunt Theobalds Grove Enfield Town Turkey Street Romford Bush Hill Park Southbury Emerson Park Upminster Edmonton Green Silver Street Chingford White Hart Lane Highams Park Watford Junction Bruce Grove Wood Street Watford Seven Sisters Walthamstow Central High Street Harringay Blackhorse Road Walthamstow Queen's Road Bushey Green Lanes Carpenders Park Crouch Hill South Tottenham St. James Leyton Midland Road Hatch End Upper () Stamford Hill Street Leytonstone Headstone Lane Holloway Stoke Newington Clapton High Road Harrow & Kentish Town West Rectory Road Wanstead Park () Wealdstone Gospel Oak Camden Road () Hackney Woodgrange Park () Kenton () Caledonian Road Canonbury Downs Barking South Kenton & Barnsbury Barking Riverside () North Highbury & Islington Dalston Kingsland Hackney Central Wembley Hampstead Heath Dalston Wembley Finchley Road & Frognal () Junction London Fields Central West Hampstead ( ) Haggerston Cambridge Homerton Stonebridge Brondesbury Hoxton Heath Hackney Wick Park Brondesbury Park Shoreditch High Street Bethnal Green Stratford Harlesden Kensal Rise Kensal Green Liverpool Whitechapel Willesden Queen's Park Street Shadwell () Junction Kilburn High Road Wapping South Hampstead Rotherhithe Shepherd's Bush () Euston () Canada Water Kensington (Olympia) Surrey Quays West Brompton Battersea Park Imperial Wharf () (limited service) New Cross Clapham Queens Road Peckham New Cross Gate Junction Peckham Rye Brockley Acton Central Wandsworth Road Denmark Hill Honor Oak Park South Acton () Clapham Forest Hill Gunnersbury High Street Sydenham Kew Gardens Richmond Crystal Palace Penge West Anerley Norwood Junction West Croydon ()
Legend
Station National Rail Liberty line Accessible station Thameslink Lioness line Interchange station Elizabeth line Mildmay line Accessible interchange Docklands Light Railway Suffragette line Internal interchange London Underground Weaver line Out-of-station interchange London Trams Windrush line (   ) Nearby interchange London River Services The new London Overground line names and colours were introduced across the London rail network in November 2024

v t e West London Route
Legend
Watford Junction Greater London boundary Harrow & Wealdstone Wembley Central West Coast Main Line to Euston North London line to Stratford Grand Union Canal Shepherd's Bush Kensington (Olympia) West Brompton Imperial Wharf River Thames Brighton Main Line to Victoria Clapham Junction Wandsworth Common Balham Streatham Common Norbury Thornton Heath Selhurst East Croydon Brighton Main Line and Oxted line

Main line National Rail services at Harrow & Wealdstone are operated by London Northwestern Railway and Southern.

The typical off-peak service in trains per hour is:

• 4 tph to London Euston (non-stop)
• 1 tph to East Croydon via Kensington (Olympia)
• 1 tph to Watford Junction
• 2 tph to Tring (semi-fast)
• 2 tph to Milton Keynes Central (stopping)

On Sundays, the semi-fast services between London Euston and Tring do not run and the service to East Croydon runs only as far as Clapham Junction.

Local services at Harrow & Wealdstone are operated by London Overground on the Lioness line and by London Underground on the Bakerloo line.

The typical off-peak service in trains per hour is:

• 4 tph to London Euston (all stations)
• 4 tph to Elephant & Castle (all stations)
• 4 tph to Watford Junction (all stations)

Preceding station	London Overground			Following station
Headstone Lane towards Watford Junction		Lioness line Watford DC line		Kenton towards Euston
Preceding station	London Underground			Following station
Terminus		Bakerloo line		Kenton towards Elephant & Castle
Preceding station	National Rail			Following station
Bushey towards Milton Keynes Central		London Northwestern Railway London–Milton Keynes		London Euston Terminus
Watford Junction towards Tring
Watford Junction		Southern West London Line		Wembley Central
Historical railways
Headstone Lane towards Watford Junction		Bakerloo line (1917–1982)		Kenton towards Elephant & Castle
Hatch End		London and North Western Railway West Coast Main Line		Wembley Central
Willesden		London and Birmingham Railway		Watford old station
Disused railways
Terminus		British Railways Stanmore Branch Line		Belmont

Network Rail's July 2011 London & South East Route Utilisation Strategy (RUS) recommended diverting West Coast Main Line (WCML) services from stations between London and Milton Keynes Central away from Euston, to Crossrail via Old Oak Common, to free up capacity at Euston for High Speed 2. This would provide a direct service from the WCML to the Shenfield, Canary Wharf and Abbey Wood, release London Underground capacity at Euston, make better use of Crossrail's capacity west of Paddington, and improve access to Heathrow Airport from the north. Under this scheme, all Crossrail trains would continue west of Paddington, instead of some of them terminating there. They would serve Heathrow Airport (10 tph), stations to Maidenhead and Reading (6 tph), and stations to Milton Keynes Central (8 tph).

In August 2014, a statement by the transport secretary Patrick McLoughlin indicated that the government was actively evaluating the extension of Crossrail as far as Tring, with potential Crossrail stops at Harrow & Wealdstone, Watford Junction, Hemel Hempstead, Berkhamsted and Tring. The extension would relieve some pressure from London Underground and London Euston station while also increasing connectivity. Conditions to the extension are that any extra services would not affect the planned service pattern for confirmed routes, as well as affordability.

The TfL Getting Around map shows this station as having disabled access (platform 1 does not involve the use of a lift when entering/leaving the Harrow entrance nor does platform 6 using the Wealdstone entrance).

The station is at the southern end of Wealdstone High Street; it is a short distance from Harrow Civic Centre and less than a mile from Harrow town centre. The station serves these areas as well as Belmont and Harrow Weald, both of which lack stations of their own, and parts of Headstone and Kenton. London Buses routes 140, 182, 186, 258, 340, 640, H9, H10, and night routes N18 and N140 serve the station.

Wikimedia Commons has media related to Harrow & Wealdstone station.

• Train times and station information for Harrow & Wealdstone station from National Rail
• London Transport Museum Photographic Archive
  • Harrow & Wealdstone station, Harrow building at original main entry to station, 1925
  • Harrow & Wealdstone station, Wealdstone building, 1928
  • Harrow & Wealdstone station, Wealdstone building, 1930
  • Harrow & Wealdstone station, Wealdstone building, 1956
• Europe's history of rail disasters (BBC)
• Harrow and Wealdstone Disaster