The deal, which is tied for the fourth largest contract in major league history, was completed Thursday after Cano passed his physical.
Cano had spent his entire career with the Yankees. The five-time All-Star played in 160 games last season and hit .314 with 27 homers and 107 RBIs. Cano posted a .899 on-base plus slugging percentage and finished fifth in American League MVP voting.
The Yankees offered Cano a $175 million, seven-year deal. New York went 85-77 last season and missed the playoffs for only the second time in 19 years; Seattle went 71-91 and hasn't been in the playoffs since 2001.
The 31-year-old second baseman is represented by Jay-Z's Roc Nation and CAA Sports. He was New York's most feared hitter for the past several years, and the loss of a middle infielder who bats .300 and hits 30 homers stings. Cano posted a .899 on-base plus slugging percentage last season and finished fifth in American League MVP voting.
Only the two deals signed by Alex Rodriguez — first with Texas and then the Yankees — and Joey Votto's contract with Cincinnati were worth more. Albert Pujols also signed a $240 million deal with the Los Angeles Angels. Cano will make $24 million per season from 2014-23 and the contract includes bonuses for awards. It's the fifth deal to top $200 million in baseball history.
Cano is scheduled to be introduced at a news conference later Thursday.
"We have made a major commitment to a player who is one of the most dynamic in Major League Baseball," Seattle general manager Jack Zduriencik said in a statement. "And Robinson has made a commitment to the Seattle Mariners organization and to the City of Seattle. We have stayed true to our plan of building our organization from the ground up through the amateur draft and player development, and now have had the opportunity to add an All-Star player through free agency."
Cano's been one of the most durable players in baseball for the past seven seasons, missing only 14 out of 1,120 games since the start of the 2007 season. He's a career .309 hitter who has averaged 24 homers and 97 RBIs per season. Cano has hit at least 25 homers and had a slugging percentage above .500 in every season since 2009.
Cano will be the anchor for a lineup that's lacked consistency at the plate most of the past decade. Seattle made other additions at the winter meetings to support Cano, agreeing to a one-year deal with Corey Hart and acquiring Logan Morrison in a trade with the Miami Marlins.
All of them should help an offence that between 2009 and 2012 ranked last in baseball in batting average, and was near the bottom in runs scored and homers. The Mariners showed some pop this past season with 188 home runs — second-most in baseball — but 52 of those came from the combo of Kendrys Morales and 41-year-old Raul Ibanez, both free agents.
"A player like Robinson Cano can make a manager look really smart, really quick," Seattle manager Lloyd McClendon said. "No one player is going to win a championship for you, but I would remind people that we have some pieces in place."
It's the second straight off-season Seattle will have made a massive financial commitment to a player after giving a $175 million, seven-year deal to ace Felix Hernandez last winter. Seattle has plenty of financial room to make significant cash commitments because the only major contracts on the books for 2014 are for Hernandez and Hisashi Iwakuma, and only Michael Saunders and Justin Smoak are entering arbitration.