Cano receives a full no-trade clause, a source told ESPN's Jim Bowden.
The player and his agents met Thursday night in Seattle with the Mariners' top executives, and the source said the team made them an offer they couldn't refuse.
The source said Cano, 31, will return to Seattle on Sunday and will undergo a physical Monday to complete what would be the third-largest contract in baseball history, tied with the one Albert Pujols signed with Los Angeles Angels three years ago.
Cano's representatives and Seattle general manager Jack Zduriencik did not return messages seeking comment on Friday.
"We are not able to confirm any news regarding Robinson Cano at this time. If and when an agreement is completed and finalized, we will announce," the Mariners statement read.
Alex Rodriguez has had baseball's top two contracts. In the winter of 2007, he signed a 10-year, $275 million extension with the New York Yankees. That deal replaced the 10-year, $252 million pact he signed with the Texas Rangers in December 2000, when Rodriguez left Seattle after spending his first seven major league seasons with the Mariners.
Cano's deal also would be a coup for a franchise that's gone a dozen years since making the postseason and would bring credibility to the Mariners after they struck out in the past in pursuits of big free agents like Prince Fielder and Josh Hamilton.
Cano is a five-time All-Star second baseman for the Yankees. Last season, he played in 160 games, hitting .314 with 27 homers and 107 RBIs, while posting a .899 OPS. He finished fifth in American League MVP voting.
"He was a great Yankee. He was a great player. I think everybody tried hard to get the deal done. We just never got close enough obviously. We wish him the best. We hope he had a long, healthy career," Yankees managing general partner Hal Steinbrenner said on Friday. "We're going to keep going. We're still looking at all the same guys that we were looking at a week ago or two ago. We're going to continue to improve. We're not done spending."
Helping provide room to increase the payroll is the Mariners' investment in a new regional sports network that is expected to net Seattle significant revenue in the coming years.
Information from The Associated Press was used in this report.