The deal was announced Wednesday.
Pyatt had two goals and seven points in 61 games with Montreal last season. He has played in 101 NHL games overall, picking up four goals and eight assists.
Pyatt was drafted by the New York Rangers in the fourth round of the 2005 NHL draft. The forward was acquired by Montreal, along with Scott Gomez and Michael Busto in June 2009 for Chris Higgins, Doug Janik, Ryan McDonagh and Pavel Valentenko.