In 1859, Charles, along with his elder brother John Forster Alcock, was a founder of Forest Football Club, based in Leytonstone, Essex.

As Charles Alcock would later write:[5] Just at that time [1859] a happy thought occurred to two or three old Harrovians located in the north-east suburbs of London ... to carry on the game of football which they had just had to give up on leaving school.In March 1862, both brothers played for Forest in a home 1–0 victory over Crystal Palace FC.

[6] Charles was a prime mover in the 1863 foundation of Forest's more famous successor, Wanderers F.C., who were initially a predominantly Old Harrovian side.

[13] Alcock himself was one of the earliest football players to be described in contemporary reports as showing teamwork between players, for example in the 1871 England versus Scotland international:"indeed it seemed as if the [Scottish] defence would prove more than equal to the attack until a well executed run down by C W Alcock WC Butler and RSF Walker, acting in concert, enabled the last named of the trio to equalise the score by the accomplishment of a well merited goal"[14]In 1874 Alcock was the first to advocate the predecessor of the modern passing style known as the "Combination game": "Nothing succeeds better than what I may call a 'combination game'"[15] He attributed to Sheffield FC the beginning of the modern passing game.

In a discussion on the history of a "definite scheme of attack" and "elaborate combination" in football playing style, Alcock noted (in 1891): "The perfection of the system which is in vogue at the present time however is in a very great measure the creation of the last few years.

[21] He also argued successfully for the law-change proposed by Wanderers FC to eliminate the "touch down" tie-breaker from the FA laws, and against several alterations suggested by Sheffield FC that would have introduced features from Sheffield rules football into the FA code, saying that his proposed changes would be "the only step to inducing the public schools to join" the association.

Alcock himself was categorical about the international standing of the 1870 games and where he felt responsibility lay for the inclusion of so many England-based players in the Scotland team, writing in the Scotsman newspaper:"I must join issue with your correspondent in some instances.

First, I assert that of whatever the Scotch eleven may have been composed the right to play was open to every Scotchman [Alcock's italics] whether his lines were cast North or South of the Tweed and that if in the face of the invitations publicly given through the columns of leading journals of Scotland the representative eleven consisted chiefly of Anglo-Scotians ... the fault lies on the heads of the players of the north, not on the management who sought the services of all alike impartially.

[13]Alcock then proceeded to offer further challenges with a Scottish team drawn from Scotland and proposed the north of England as a compromise venue to take into account travelling distances.

[24] Alcock appeared to be particularly concerned about the number of players in Scottish football teams at the time, adding: "More than eleven we do not care to play as it is with greater numbers it is our opinion the game becomes less scientific and more a trial of charging and brute force... Charles W Alcock, Hon Sec of Football Association and Captain of English Eleven".

Thus, the FA Cup – the world's first national football tournament, based on Alcock's experience of inter-house 'sudden death' competition at Harrow – was born.

The final was played at The Oval, the home ground of Surrey County Cricket Club, of which Alcock had become Secretary of the previous month.

Following a controversy over the expulsion of Preston North End from the 1883–84 FA Cup over alleged financial inducements to Scottish players, Alcock worked to introduce a regulated professionalism into the game.