The 21-year-old forward, who was a restricted free agent, had 18 points (seven goals, 11 assists) in 43 regular-season games for the Rangers last season and five points (two goals, three assists) in 19 Stanley Cup Playoff games.
Selected by New York with the No. 2 pick of the 2019 NHL Draft, Kakko has 58 points (26 goals, 32 assists) in 157 regular-season games and five points in 22 playoff games.
The Rangers (52-24-6) lost in six games to the Tampa Bay Lightning in the Eastern Conference Final last season. They agreed to contracts with center Vincent Trocheck (seven years) and goalie Jaroslav Halak (one year) in free agency.
Forwards Ryan Strome (Anaheim Ducks), Frank Vatrano (Ducks), Andrew Copp (Detroit Red Wings), and defenseman Justin Braun (Philadelphia Flyers) left in free agency, and goalie Alexandar Georgiev was traded to the Colorado Avalanche on July 7.
