Gunnarsson, 26, had one goal and 14 assists in 37 games last season.
In 224 career regular-season games, all with the Leafs, Gunnarsson has registered 12 goals and 57 assists with 58 penalty minutes.
The Leafs originally selected the six-foot-two, 196-pound Swede 189th overall in the 2007 draft.
Meanwhile, the Leafs announced Monday that they have agreed to an affiliation with the Orlando Solar Bears of the ECHL. The Leafs will share the affiliation with the Minnesota Wild.