Larsson played his part in Birmingham's run to the 2011 League Cup Final. He scored from the penalty spot before Nikola Žigić headed an 84th-minute winner in the quarter-final against local rivals Aston Villa. In the first leg of the semi-final against West Ham United, Liam Ridgewell scored from Larsson's corner before Victor Obinna was sent off for kicking Larsson in the groin in an off-the-ball incident. Despite speculation over his future at Birmingham – with his contract due to expire at the end of the season, his advisor was given permission to talk to Newcastle United about a proposed move during the January transfer window, but personal terms were not agreed, and the player was booed when he came on as a substitute in the previous game, against Manchester United – Larsson returned to the starting eleven in place of the cup-tied David Bentley and played 100 minutes as Birmingham overturned a 2–1 deficit to win the semi-final 4–3 on aggregate. Roger Johnson flicked on Larsson's corner for Žigić to give his team an unexpected lead in the final at Wembley against firm favourites Arsenal. Though Robin van Persie equalised, Obafemi Martins scored an 89th-minute winner to give Birmingham their first trophy since 1963 in what the "Daily Mail" described as "the biggest upset at Wembley since Wimbledon beat Liverpool to the 1988 FA Cup."