The 34-year-old veteran has only appeared once for the Loftus Road club this season, and that was a 4-0 FA Cup defeat by Everton in early January.
He joined QPR in August 2012 and was first choice for Harry Redknapp's side last season.
Toronto's general manager, Tim Bezbatchenko, told the franchised team's website: "Adding a player of Julio Cesar's experience and ability only strengthens our club both in the short and long term.
"We are committed to creating a culture of winning at TFC, and there are few people in the world of soccer with a proven track record of consistently getting results that Julio has. We are very excited to bring him to Toronto FC."
He also played for Italian side Inter when they won both the Champions League and World Club Cup in 2010, the year he was voted UEFA goalkeeper of the year.
Cesar has collected 77 caps for his country and was part of Brazil's squad in two World Cup Finals tournaments.
Cesar was recently named in Luiz Felipe Scolari's provisional Brazil squad for the forthcoming friendly against South Africa on March 5, and he hopes to play in this summer's World Cup finals in his home country.