The Timbers trailed 1-0 at half-time to Colorado Rapids but goals to Maxi Urruti and Diego Valeri in the final 20 minutes saw the home side triumph in Portland for the first time in four games in all competitions.
Urruti finished off a flowing passing move in the 72nd minute, while Valeri produced a stunning strike with 13 minutes left to give the hosts victory.
The win took Portland to 24 points in the Western Conference, which saw them rise above Chivas USA into seventh, while Colorado stretched their winless streak away from home to six games.
The Rapids hit the front in controversial fashion at Providence Park, with Deshorn Brown scoring during a goal-mouth scramble in the 16th minute.
Drew Moor headed Dillon Powers' corner on target but Portland goalkeeper Donovan Ricketts did well to save that and a follow-up from Brown, before the officials judged another effort from the Jamaican striker had crossed the line, even though Valeri attempted a last-ditch clearance.
The Timbers had over 60 per cent possession for the match but had to wait until deep in the second half to produce a comeback.
An impressive passing move in their attacking half ended with right-back Jack Jewsbury cutting the ball back for Urruti, who stabbed his shot past Rapids keeper Clinton Irwin, before Valeri unleashed from 25 yards into the top corner, as the Timbers supporters erupted.
The victory was welcome relief for the home crowd, who have only seen Portland win five of 20 home games in MLS this season.
Despite the loss, Colorado (28 points) remain second in the West, 10 behind the conference-leading Seattle Sounders.
