Out of contract at the end of the 2009–10 season, Ledley entered into talks with several clubs, including Stoke City, West Bromwich Albion and AS Roma, before eventually joining Scottish Premier League side Celtic on a four-year contract on 12 July 2010. He made his competitive debut for the club on 28 July in a 3–0 defeat to Braga in the first leg of the third qualifying round of the UEFA Champions League, before making his SPL debut two weeks later in a 1–0 win over Inverness Caledonian Thistle.