The current club was formed in 1926, following several other outfits that had carried the town’s name in earlier years, the first known, Northwood FC, being formed in September 1899, but it is not clear how long they existed. A team called Northwood Rovers played in the Harrow & District League up to the First World War, but a new Northwood FC was launched after the conflict, in September 1919, and soon Emmanuel Northwood were also competing in the Harrow & District League.

The next club to commence was Holy Trinity Northwood, again in the Harrow League, whilst in 1922 Northwood moved to the Uxbridge & District League. However, having lost their first nine fixtures in the second season, Northwood found that they were unable to field a team for later games and the club folded. Around the same time, Emmanuel Northwood also withdrew from the Harrow League.

After two seasons in which just Holy Trinity represented the town on the football field, a few people who had been involved with the two failed set-ups decided to form a new club, and Northwood United was launched for the 1926-27 campaign, with Leslie Faint, secretary of the previous Northwood FC, holding the same post for United. The Rev. L. Gordon M. Sheldon from Emmanuel arranged with Ruislip-Northwood Council for the use on alternate weeks (St John's Old Boys FC also played there) of the pitch at Northwood Recreation Ground, at a cost of 2s 6d per match.

For the first two seasons, just friendly matches were played, apart from entering the Northwood Hospital Charity Cup, but after the second campaign, in which sixteen of the twenty-three games had been won, it was decided to join a league.

Northwood United were elected to Division Two of the Harrow & District League for 1928-29, playing at the new Northwood Playing Fields, which was adjacent to Haste Hill golf course, at the end of The Drive, Northwood. In the team at that time were young players Joe Gill, Bob Bell and Tom Bell, who would be with the club many years later, even returning after the Second World War, and the latter also became club secretary.

In their second year the club gained promotion, and twelve months later, further success saw them move up to the Premier Division of the Harrow & District League (later renamed Harrow, Wembley & District League). At that time the club gained the use of a pitch in Northwood Recreation Ground at an annual cost of £14. 14s. including pitch marking and dressing room.

1931-32 saw the commencement of Northwood United’s dominance of local junior football. Within five years of entering league football, United had become Premier Division champions, a feat they repeated for each of the next four years, followed by second and third places up to the War. The League Senior Challenge Cup was won three times during that period, and in 1938 the club won the Middlesex Junior Cup - defeating Metropolitan Water Board 4-2 in the final at Hayes FC - after having been losing finalists in 1935 and 1936.

After the Second World War, with the disappearance of the Holy Trinity Northwood team, the club dropped the United suffix from their title, and were Harrow & Wembley champions in consecutive years, 1948 and 1949.

After being a mid-table side in the Premier Division throughout the ‘fifties, the club hit a slump in the early 'sixties, suffering a first-ever relegation in 1962, and they became something of a yo-yo side for a few years, but towards the end of the 1960s things improved. Northwood were elected into the Middlesex League in 1970, and they became runners-up at the end of their second season.

Having played in the main park since 1931, the mid-seventies saw the Woods develop an area of rough land into their present ground with suitable facilities, and further developments have been carried out regularly since.

The Woods won the Middlesex League Cup on three occasions and also the League championship in 1978, completing the Middlesex League double, and the club were subsequently elected to the Hellenic League. In the first season they were promoted to the top flight as Division One champions and Hellenic League Division One Cup winners. Northwood also lifted the Middlesex Intermediate Cup by beating Feltham 2-1 – the club’s first County Cup success for forty-one years. Floodlights were erected and senior status was granted in 1981. 

Due to large travelling costs, Northwood switched to play in the London Spartan League in 1984 and they were soon to become one of the competition's top clubs. After one League Cup win, a runners-up spot and two third places, the Woods completed a League and Cup double in 1992. Along with this success came considerable ground improvements, which allowed them to be promoted to the Isthmian League, Division Three.

After five years at the higher level, following early success by winning the 1993 Associate Members Trophy, and several promotion challenges, Northwood made it to Division Two in 1997. Following three seasons in that division, the Woods earned further promotion when they gained the runners-up spot in 2000. They also captured the Associate Members Trophy for a second time and reached their first ever Middlesex Senior Cup final, where they went down 2-0 to GM Vauxhall Conference outfit Hayes.

Another three years later and Northwood found themselves in the Premier Division, having won the Division One North championship in 2003. They also captured the Isthmian League Cup for the first time in 2002, beating Premier Division Hampton & Richmond Borough in the final, 3-2 after extra-time, and also reached the Middlesex Senior Cup final once again, this time beaten in extra-time by Hendon.

September 2002 saw the Woods defeat Premier Division champions Gravesend & Northfleet 4-2 to lift the Isthmian Charity Shield. It proved a difficult first season in the Premier Division, but after an F.A. restructure of non-League football, Northwood remained in the division for a second season.

In 2003, Northwood received the prestigious award of Community Club status from the Football Association in recognition of the club's commitment to youth football in the area – the club have teams of all age groups playing their football within the confines of Northwood Park. Improvements have been made to the standards in recent years, and the club is hoping this will result in many youngsters developing into first-team players in the future.

Northwood faced a new challenge for the 2005-06 campaign, having been moved to the Southern League Premier Division, and although the first season in the new league was a struggle, the team avoided the drop on the final day. However, 2007 saw the Woods finish in 22nd place in the division, and relegation followed – the first time the club had faced demotion in senior football. It wasn't all doom and gloom, though, as under manager Colin Payne, Northwood lifted the Middlesex Senior Cup for the first time in their history by defeating Hayes, of the Conference South, on their own ground in the final.

Having been moved back to the Isthmian League for the 2007-08 campaign, and after spending three years in Division One North, Northwood were then transferred again to the Southern League Division One Central in 2010-11. The following season was boosted by an FA Cup run to the third qualifying round while a forced change of manager saw the Woods have to rebuild the squad so a mid-table finish was very acceptable. Mark Burgess had successful five seasons in charge, surpassing expectations by finishing ninth, tenth and then seventh respectively.

Since then, a series of managers have come and gone quickly and Scott Dash, who was appointed permanently in December 2018 following a successful spell as caretaker only lasted just under a year after a series of poor results saw another change and the arrival of Jamie Leacock to the role. Jamie's tenure was ended in January 2020 after a run of ten successive defeats and former player Robert Ursell was placed in charge. His time was interrupted by the pandemic and then resigned his position in April 2021.

The new man to steer the Woods to a more competitive position in the Isthmian League was to be former Ashford Town boss Ben Murray but after the club's worst start ever to a season, he was replaced in November 2021 by Director of Football Steve Ringrose and Head Coach Ben Bukowski along with Player-Coaches Andy Lomas and Keagan Cole. Their impact was instant, winning a club record eight away games in succession, a run that lifted the side to the safety of mid-table.

The improvement continued in the 2022/23 season, leading the South Central division for several months before eventually qualifying for the end-of-season play-offs for the first time in the club's history. Though they were beaten 2-1 at eventually promoted side Walton & Hersham, it had been their best season for some time.

With manager Ben Bukowski having left the club, the 2024/25 campaign saw the Woods shifted back once more to the Southern League, Division One Central.