Mauro Diaz scored a late winner to lift Dallas above Portland and continue the Timbers' winless start.
A pair of red cards in the first half cost each side a player. An off-the-ball incident between Michael Harrington and Je-Vaughn Watson ended in fisticuffs and a pair of ejections.
The home side scored the game's first goal in the dying moments of the first half. Jair Benitez came forward and launched a high cross across the penalty area that Kelyn Acosta headed back down into the middle. Unmarked, Blas Perez had an easy header to score.
A fortunate deflection leveled the game at 1-1. Max Urruti's attempted pass was cut out by Matt Hedges, but it went off the Dallas defender's foot and looped over the head of goalkeeper Chris Seitz.
But Portland's luck wouldn't hold out. Mauro Diaz scored a winner for Dallas in the 84th minute, collecting, turning and shooting after a poor Timbers clearance on an FCD free kick allowed the hoops to sustain pressure.
Portland is now a worrying 0-2-2 on the year, while Dallas has rocketed out to 3-0-1 start and first place in the Western Conference.