It was a matchup of the two last-place clubs in MLS.
Portland took the lead in the opening half on a score from Sal Zizzo, but Toronto produced tallies 6 minutes apart in the second half by Eric Hassli and Luis Silva.
Nagbe's game-tying goal was his fourth of the season.
Portland is 5-12-6 and Toronto is 5-13-5. Portland's goals were just the third and fourth the Timbers have scored on the road all season.