The Bruins jumped past Montreal into the lead in the Northeast Division and took over the second-seeded position in the Eastern Conference playoff race.
Boston grabbed a 4-0 lead before the Devils made it close in the third period.
Seguin's goal boosted the Boston lead to 5-3 and New Jersey threw a brief scare into the Bruins when Matt D'Agostini scored with 37 seconds to play.
Anton Khudobin protected the lead the rest of the way and made 24 saves in the victory.
New Jersey has gone 0-4-4 in its last eight games to drop four points out of a playoff position. Martin Brodeur was touched for all five goals on a mere 18 shots.