On December 15, 2009, Leighton was brought back to the Flyers when they claimed him off waivers to back up Brian Boucher while Ray Emery recovered from injury. On December 21, Leighton was given a starting role when Boucher suffered an injury. On January 1, 2010, he started in goal for the Flyers for the 2010 Winter Classic. During a playoff game against the Boston Bruins, Leighton stepped in for an injured Boucher to play in his first ever NHL playoff game where he helped keep Boucher's shutout in a 4-0 win. During the 2010 Eastern Conference Finals against the Montreal Canadiens, he only let in 7 goals in five games and recorded 3 shutouts as the Flyers advanced to the Stanley Cup Finals to face the Chicago Blackhawks. Leighton started all six games of the Finals but struggled where he recorded a goals against average of 3.96 and a save percentage of 0.876. Leighton was the losing goalie in game 6 when the Blackhawks defeated the Flyers four games to two which ending with an overtime goal by Patrick Kane.