Toronto was 9-0-9 in its previous 18 games but fell one game short of tying the mark of the Columbus Crew (July 3, 2004-April 2, 2005) and FC Dallas (May 27-Oct. 9, 2010).
The last Toronto regular-season loss was 2-0 at the New York Red Bulls on Aug. 3, 2019. The streak began a week later with a 1-1 draw at Orlando City.
A half-hour after Camacho gave Montreal the lead, the first half ended on a weird note.
Toronto forward Jozy Altidore, who did not play in the team's 1-0 victory over Montreal on Friday because of personal reasons, drew a penalty from Camacho in the 44th minute.
Alejandro Pozuelo, who had the entry ball to Altidore and scored the only goal Friday via a penalty, once again stepped to the spot.
Instead of shooting, he attempted a trick play from the penalty spot and tapped the ball to Pablo Piatti, who scored, but it backfired and Montreal was given a free kick, possibly because of encroachment. Toronto coach Greg Vanney wasn't sure.
"I thought if we were in the box or somebody was in the box it would be retaken," he told TSN at the half. "Maybe because it was an attacking player it doesn't get retaken. I don't know."
After the game, Vanney bemoaned the incident as having cost his side at least a point.
"We're down a goal, we should just be burying the ball in the back of the net and moving on," he said. "We gift them the fact that they don't even have to make a save or do anything on a penalty kick, and we have a number of other opportunities [after]."
Camacho's goal ended Toronto's club record shutout streak at 374 minutes.
The defender's first goal of the season came after a corner kick went to Romell Quioto. Quioto whipped the ball into the box, and Camacho went above defender Justin Morrow to head the ball to the back post.
It was the first time Toronto trailed in a regular-season game this year.
Toronto plays Saturday at Vancouver. Montreal hosts Toronto on Sept. 9.