Boucher raised his season's record to 12-6-2 and was especially effective in the second period, when he stopped 13-of-14 shots, as the Flyers improved their lead over idle Pittsburgh to three points in the Eastern Conference.
Dallas, which lost for the fifth time in six games, got its only goal from Brenden Morrow.
Kari Lehtonen let in three scores on 32 shots.
Philadelphia leads the Eastern Conference with 75 points, six better than Tampa Bay. Dallas is in third place in the Western Conference, 12 points back of Vancouver, which has an NHL-best 77 points.