The 23-year-old Janson has spent the past six seasons at Tigre, where he has made 10 goals and 10 assists over 82 league appearances. He was part of the Tigre squad that finished as runners-up in the 2012 Copa Sudamericana to São Paulo of Brazil.
“Lucas is a young, dynamic player that has the ability to play out wide, up front and centrally as an attacking midfielder,” Toronto GM Tim Bezbatchenko said in a statement. “We wanted to bring in a player that gives us multiple options in the attack and Lucas fits that need. We are excited to bring him in on loan and get him integrated into the group.”