Their performance slipped the following season, and as a result, they failed to qualify for play in the Gauliga Baden, one of 16 new regional top-flight divisions formed in the reorganization of German football in 1933.

They were also part of that league from 1941 to 1944, until it was reduced to a rump circuit in 1944–45 when the region fell to advancing Allied forces in the latter stages of World War II.

Following the conflict, occupying Allied authorities disbanded organizations across the country, including football and sports clubs, as part of the process of denazification.

FC's eighth-place finish in that campaign was not good enough to qualify the side for continued Oberliga play and they slipped into the Amateurliga Südbaden (II).

Another relegation followed in the 2015–16 season, now to the Kreisliga A. FC Rastatt has been one of the most successful clubs in the South Baden Cup, having won the competition five times, in 1946, 1973, 1977, 1981 and 1984.