The deal is with sports streaming service DAZN and means an average take of $33 million per fight.
Alvarez's fights have always been shown on HBO thanks to the premium cable network's agreement with Oscar De La Hoya's Golden Boy Promotions.
"Being part of this historic deal will require me to prepare myself even more and offer fans even better performances", he added.
De La Hoya is expected to announce the deal at Wednesday's press conference in NY to promote Alvarez's December 15 return at New York's Madison Square Garden when he moves up in weight to challenge secondary WBA super middleweight titleholder Rocky Fielding in the first bout of his new DAZN deal. Golden Boy Promotions is one of boxing's most active and respected promoters, presenting shows in packed venues around the United States on networks such as HBO, ESPN, ESPN Deportes, EstrellaTV and the newly announced partnership with DAZN.
"This is only from my hard work", said Alvarez, speaking to ESPN after signing the contract.
The reported value of the deal would top the previous most-valuable contract - the $325m 13-year deal of baseball star Giancarlo Stanton in 2014. "The most important thing to me was being able to give the fans the opportunity to see me fight without having to pay the US$70 or US$80 for my fights on pay-per-view".
First off, in recent years to watch a Canelo fight in America, you would have had to shell out big bucks to buy one of his fights on pay per view.
The 28-year-old is set to fight Britain's Rocky Fielding on December 15 but he still has eyes on putting right that loss, the only one in 53 career fights. "DAZN has the flawless platform to make this dream come true, and with the biggest star in the sport at the helm of this journey, I have no doubts that we will succeed in unimaginable ways". "I know how important I am to any platform I go to".
"I've always liked a challenge, and this is yet another challenger in my career", said Canelo Alvarez.
Under the deal's terms, Alvarez, who owns a 50-1-2 record as a professional boxer, will fight on DAZN's streaming platform, which recently launched in the U.S. The platform charges a $9.99 monthly fee for access to combat sports events around the world, including Bellator MMA. Now Alvarez will seek to join a small and illustrious list of three-division world champions from Mexico as he steps up to 168 pounds to challenge Fielding.