At the start of the 2009–10 season, Abdou scored in Millwall's first game of the season against Southampton, with a header, it turned out to be his only goal of the season. However, shortly after, he suffered an injury during a 4–0 win over Bournemouth and was sidelined for weeks. Abdou made his return from injury, starting the whole game, in a 1–1 draw against Brighton & Hove Albion on 29 August 2009. His performance saw him signed a contract extension, keeping him until 2013. During a 4–4 draw against local rivals’ Charlton Athletic on 19 December 2009, Abdou was sent–off for a professional foul in the 37th minutes, for giving a penalty, resulting in Charlton successfully converting the penalty. But he did not serve a match ban and returned in a next match on 26 December 2009 against Norwich City, which they lost 2–0. Abdou continued to establish himself in the first team, playing in the midfield position for the rest of the season and later helped play a big part in earning Millwall promotion later in the 2009–10 season. Millwall were eventually promoted after beating Swindon Town in the play-off final. At the 2009–10 season, Abdou went on to make fifty–two appearances and scoring once for the side.