Westminster has an historic joint claim to a major role in the development of Association Football, which remains the school's largest sport.

During the 1840s at both Westminster and Charterhouse, pupils' surroundings meant they were confined to playing their football in the cloisters, making the rough and tumble of the handling game that was developing at other schools such as Rugby impossible, and necessitating a new code of rules.

By 1867 the Football Association had chosen in favour of the Westminster and Charterhouse game and adopted an off-side rule that permitted forward passing.

In 1861 for instance an eleven from Trinity College, Cambridge, eight of whom were Old Westminsters, returned to their alma mater for a friendly match.

With the FA Cup being run on a regional basis until the latter rounds, the Old Westminsters were often the best side from the capital, reaching the quarter-final on three occasions.

The club was exempted again for the next two years, losing to Stoke in 1889–90 and scratching to West Bromwich Albion in 1890–91 after being unable to raise an eleven,[16] and, once the exemption was over, won through to the first round proper in 1891–92; yet again the club was drawn against West Bromwich Albion, but this time at home, so the game took place at the Oval, in front of a crowd of 6–7,000.

[18] At the amateur level, the club was originally very successful, winning the London Senior Cup in 1887 (joint winners), 1888, 1890, 1892 and 1893.