The 29-year-old Convey was acquired by Sporting KC from the San Jose Earthquakes in December 2011. He appeared in 20 MLS matches for the club, scoring one goal and making two assists.
Convey began his MLS career with DC United, and helped English club Reading secure promotion to the English Premier League in 2006.
He's also made 46 appearances for the U.S. national team, scoring the deciding goal in a 3-2 victory over Costa Rica in the third-place game of the 2003 Gold Cup.
Convey, a three-time MLS all-star, has made 189 appearances with 14 goals and 33 assists in 10 MLS seasons.
"This is a good mid-season deal for Toronto FC," Toronto president and general manager Kevin Payne said in a statement. "We are in need of quality MLS players on our team and Bobby fits the bill perfectly.
"I've known Bobby since he was a 16 year old rookie in MLS; and literally living in the basement of my home. He can be a very influential player in MLS and we look forward to him helping us move forward in the league."