After the 2009–10 season, Lille OSC made a €2 million (£1.7 million) offer for Landreau who wanted him to replace the veteran goalkeeper Grégory Malicki who left Lille to join Dijon on a free transfer and was the first choice goalkeeper for Lille in the 2008–09 season. The move was agreed and was completed. Five days after signing for Lille, he suffered a massive blow by damaging cruciate ligaments during a training session which kept him out of action for around six months. During his absence due to injury, Ludovic Butelle got more playing time and played about 10 matches until Landreau returned and he later became the first choice-goalkeeper ever since. On 22 October 2009, Landreau was back on the bench in Europa League during the match against Genoa (3–0) and made his league debut for Lille in a 2–0 win over Grenoble on 30 October 2009.