In 1969 Swindon defeated Arsenal 3-1 to win the League Cup for the first occasion and only time in the club's history. As winners of the League Cup, Swindon were confirmed of a place in their first European competition: the Inter-Cities Fairs Cup.
Following management switches, Swindon had a long unsuccessful era culminating in them being demoted in 1982 to the Fourth Division, the lowest professional Football League at the time. They were eventually promoted as champions in 1986 with the club achieving a Football League record of 102 points, the first club to net in over 100 points in a season. A year later they won the Second Division play-offs to achieve a second successive promotion. Promotion campaign Manager Lou Macari left in 1989 to take charge of West Ham United with veteran midfielder, and former Argentine international, Ossie Ardiles replacing him. In his debut season Swindon were Second Division play-off winners, however the club later admitted 36 charges of breaching league rules, 35 due to illegal payments made to players, and were relegated to the Third Division — giving Sunderland promotion to the First Division and Tranmere Rovers to the Second Division. A later appeal saw Swindon being allowed to stay in the Second Division.