Abdou made his Millwall debut, starting a match before being substituted in the 75th minutes, in a 4–3 loss against Oldham Athletic in the opening game of the season. Since joining Millwall, he quickly became a fan favourite among Millwall's supporters. Abdou's signature has turned out to be something of a coup for manager Kenny Jackett. In spite of one or two short-term injuries, Abdou has been successful at Millwall, holding down a regular first team slot in central midfield when fit. It was not until on 11 October 2008 when he scored his first Millwall goal, in a 3–1 win against Tranmere Rovers. However, in a 1–0 win over Hereford United on 28 October 2008, Abdou was sent–off in the 49th minutes for a "double-footed lunge" on Clint Easton and served a two match suspension. He made his return from suspension on 22 November 2008, coming on as a second-half substitute, in a 0–0 draw against Leyton Orient. At the beginning of January, Abdou missed three matches through injury and made his return on 17 January 2009, coming on as a substitute in the second half, in a 1–0 win over Tranmere Rovers. He later scored twice for the club, in a 4–2 loss against Bristol Rovers on 18 April 2009. Abdou scored the winning goal in the League One Playoff Semi-finals against Leeds United at Elland Road on 14 May 2009 to send them to Wembley for their first ever playoff final, which they lost 3–2 to Scunthorpe United. Abdou later reflected that scoring against Leeds United was a turning point of his career. After missing out on promotion during the 2008–09 season, he went on to make forty–three appearances and scoring four times in his first season at Millwall.