Nagbe headed home a cross from Steven Smith past Milos Kocic to cancel out second-half goals from Toronto strikers Luis Silva and Eric Hassli.
Silva gave Toronto FC the lead in the 63rd minute after some great work down the left side from Astone Morgan. The defender sent a cross in that was flicked on by Hassli and buried by Silva from in tight past goalkeeper Donovan Ricketts, making his Portland debut following a trade from Montreal.
Portland's Sal Zizzo put the Timbers up 1-0 in the 21st minute. After David Horst's header following a corner was cleared off the line by a TFC defender, Zizzo pounced on the loose ball from a yard out for his first goal of the season.
Hassli, making his first appearance at BMO Field since being acquired from Vancouver last month, tied the score in the 57th minute on a rebound off a shot from Silva.
Hassli was mobbed by his teammates before running to the sidelines to hug Toronto FC coach Paul Mariner.
Toronto (5-13-5) still sits last in the overall standings, a point back of Portland (5-12-6).
The Timbers nearly doubled their first-half lead in the 50th minute when Zizzo's free kick from the left flashed just wide of Kocic's goal.
Ricketts then saved Harden's looping header in the 55th minute as Toronto tried to push more players forward looking for the equalizer.
Chris Boyd found himself in alone on Kocic in the 70th minute, but the Toronto FC goalkeeper came up with a big save.
Hassli had the Reds' best chance of the first half. The Frenchman took a flick on from Luis Silva, fought off two defenders before getting a shot that seemed to fool Ricketts, who could only push the ball on top of his net.
NOTES: Toronto FC midfielder Aaron Maund made the first MLS start of his career. ... Toronto FC's next game is Saturday at home against Sporting Kansas City. ... Portland is at New York on Sunday. ... Toronto midfielder Matt Stinson (quadriceps strain) did not play and is expected to miss up to a month. ... Toronto striker Danny Koevermans underwent surgery to repair his injured left knee in Toronto on Tuesday. The Dutchman tore his anterior cruciate ligament against New England last month and isn't expected back until next May. ... Attendance was 18,773
- Toronto FC
- Portland Timbers
- Luis Silva
- Eric Hassli
- Donovan Ricketts