The 1950s and 1960s were highly successful years for FFK. The club secured the league title six times – back to back in 1950–51 and 1951–52 – and finished in second place seven times. The Norwegian Cup was won four times. In 1957, a new milestone was achieved when FFK won their second double. As league champions in 1960, Fredrikstad entered the European Cup as the first team from Norway, sensationally defeating Ajax 4–3 at home and drawing 0–0 in Amsterdam, in the first round.