They quickly became a strong regional side, playing in the Südkreis-Liga, and won the national title in 1909, defeating defending champions Viktoria 89 Berlin 4–2 in the championship final that season.

It was as Phönix Karlsruhe that the club joined the Gauliga Baden, one of 16 top-flight divisions created in the re-organization of German football under the Third Reich.

After World War II in 1946, Phönix re-emerged to compete in the newly formed first division Oberliga Süd, finishing 15th in their first season there.

As war overtook the country, the Gauliga Baden was sub-divided at various times into a number of more local city-based circuits, and the team was able to earn three second-place finishes in divisional play.

They generally competed as a mid-table side here with the exception of a strong performance in 1951 when they narrowly missed an advance to the national championship rounds after earning a third-place result just a single point behind SpVgg Fürth.

KFC Phoenix and VfB Mühlburg united to form the Karlsruher Sport-Club Mühlburg-Phönix e. V., on 16 October 1952 and the new team earned good results throughout the remainder of the decade.

Their record earned them admission as one of sixteen founding clubs into Germany's new professional football league, the Bundesliga, when it began play in 1963.

Under the guidance of new coach Winfried Schäfer, KSC's return to the top flight was marked with some success as for the first time, the team managed to work its way out of the bottom half of the league table.

In the 1993–94 season, the club had a successful run in the UEFA Cup, going out in the semi-finals on away goals to Austria Salzburg after beating, in turn, PSV, Valencia, Bordeaux and Boavista.

Their 7–0 second-round victory over Valencia, a top team in the Spanish La Liga at the time and in historical terms as well, might be considered the high point of the club's history in its centennial year.

The club started the 1997–98 Bundesliga season well, with two wins and a draw in their opening three matches, but their downfall began with a 1–6 defeat to Bayer Leverkusen on Day 4.

At the league winter break the club sat outside the relegation ranks, but a series of negative results pushed them down to 15th place until the second-last matchday of the season.

The club needed an away draw against Hansa Rostock on the final day of the season to avoid relegation but lost the match 2–4 while Borussia Mönchengladbach beat VfL Wolfsburg 2–0 to overtake KSC and finish 15th on goal difference.

After four seasons of mediocre play that saw KSC narrowly avoid being sent further down, the team turned in a much-improved performance and earned a sixth-place result in 2005–06.

[2] KSC maintained its dominance over the course of the season, playing 14 matches (nine wins, five draws) before suffering their first loss of the campaign at the hands of Erzgebirge Aue.

In their return season to the Bundesliga in 2007–08 they finished 11th, fading in the second half of the year after a strong start that saw them positioned in the qualifying places for European competition.

[5] After many restrained years, in which the targeted promotion was clearly missed, the already greatly reduced second team was discontinued for financial reasons at the end of the 2017–18 Oberliga season.