Agent Patrick Morris confirmed the signing Friday, shortly before the noon start of the NHL's free-agency period.
McCormick has six-plus years of NHL experience and earned a regular role in the Sabres lineup last season, in which he had eight goals and 12 assists for 20 points in 81 games - all career bests.
The Sabres initially signed him as a free agent in August 2009. McCormick spent the next season in the minors before appearing in three playoff games with Buffalo in 2010. He previously spent parts of five seasons with Colorado.
Overall, he has 50 points (17 goals, 33 assists) in 271 NHL games.