O'Byrne has a goal and three assists in 34 games this season for Colorado, which currently owns the worst mark in the NHL.
The 28-year-old O'Byrne joins a Maple Leafs squad that's in the thick of the Eastern Conference playoff chase. He could help add more defensive stability to a team that's surrendering an average of 2.67 goals a game.
Colorado originally acquired O'Byrne from Montreal on Nov. 11, 2010. He was taken by the Canadiens in the third round of the 2003 draft.
The Leafs also announced the signing of defenseman Andrew MacWilliam to a two-year entry level contract. MacWilliam, 23, was selected by Toronto in the seventh round of the 2008 draft.