Coming off their best performance of the season, the Union weren't able to sustain the effort against one of Major League Soccer's hottest teams.
A week after a 4-0 win at New England, the Union had several defensive miscues during a 3-1 loss Saturday night to sizzling Toronto FC before 18,271 at Talen Energy Stadium.
The Union (9-9-7, 34 points), fell to 7-3-3 at home.
Toronto is 5-0-1 in its last six MLS games and improved to 11-7-7 for 40 points, one behind Eastern Conference leader New York City FC.
"I think we gave up some pretty soft goals as a team, but it is just one game," said midfielder Alejandro Bedoya, playing his first home game for the Union after debuting in New England.