The Impact scored early but couldn't hold on as Dallas started 2014 on a positive note.
Montreal found itself ahead just ten minutes into the game. Coming down the right wing, Justin Mapp drew several Dallas defenders to him, allowing Sanna Nyassi to sneak in unmarked and easily finish Mapp's eventual cross.
Dallas pulled one back just a few minutes later, Fabian Castillo finishing a ball in the box that bounced off teammate Blas Perez.
The Hoops then took the lead in the 24th. Jeb Brovsky was judged to have pushed Mauro Diaz from behind inside the box, and Perez blasted home from the spot to make it 2-1.
Diaz himself scored the third for the Texas side, netting a free kick from just outside the 18-yard box shortly after the restart.
That goal gave Dallas a needed cushion, since Andrew Wenger pulled the Impact to within one with his 65th-minute header, leaping to meet Felipe's cross and redirecting it with power.