The club hosted, in 1921, one of the early tennis majors: the World Covered Court Championships, won by William Laurentz that year.

The club's official four founders were printer F. V. Levison, treasurer August Nielsen, and wholesalers Carl Møller and E. Selmer.

[3] KB were the pre-tournament favourites and lived up to it by comfortably winning the tournament, beating BK Haabet in the final on 29 April 1888 with a resounding 14–0 victory, scoring 40 goals in total and not conceding a single one.

Markus), which in 1910 was the home ground for Denmark's first international football match under DBU auspices, a 2–1 win over England Amateurs.

[5] The Danish Football Association (DBU) was founded by Frederik Markmann in May 1889, a former cricket and tennis player who, among other things, had been a co-founder and chairman of KB.

In the same year, DBU organized the first edition of Fodboldturneringen, which was held between 1889 and 1903, with KB winning on four occasions, including back-to-back titles in 1896–97 and 1897–98.

In 1908, when Denmark made their international debut at the Olympic Games, the club provided seven players to the 17-man squad, three defenders (the Middelboe brothers, Einar, Nils and team captain Kristian), three forwards (Oskar Nielsen, Rasmussen and Wolfhagen) and the team's goalkeeper Ludvig Drescher, of which six started in the final against Great Britain in a 0–2 loss.

[citation needed] Later in the year, an audience record for a football match in Denmark was set with 11,233 spectators when a selected Copenhagen team with six KB players met the Scottish champion Rangers FC from Glasgow, who won by the score of 4–1.

[citation needed] This attendance record only lasted three years, until Denmark met England Amateurs on 5 June 1914 and won 3–0 in front of 18,500 spectators in Idrætspark.

[8] Denmark national football team all-time top scorer Poul Nielsen (1891–1962) played for KB during all of his career.

In the late 19th century, KB established a large tennis facility called Porcelainsfabrik, which in 1902 laid the courts for the first major international tournament in Denmark.