There's an opt-out and a full no-trade clause plus a sixth-year option in the contract, sources said.
The Diaz deal is the first nine-figure contract ever for a closer, and for the first time, it takes the position into the $20 million-plus range.
Diaz, who made $10 million this year, earned the big payday after a dominant 2022 season that saw him finish with 32 saves, a 1.31 ERA and 118 strikeouts in 62 innings for a Mets team that won 101 games.
New York's bullpen finished 10th in the majors in ERA, and its top relievers in innings pitched (Adam Ottavino, Seth Lugo, Trevor Williams and Diaz) were among the 131 players across the major leagues who were declared free agents Sunday, the day after the 2022 season ended.
Keeping Diaz, 28, is a massive move for the Mets to start the offseason, as one of baseball's top free agents is now off the board.
Diaz was part of a blockbuster trade with the Seattle Mariners in December 2018, one that saw him and veteran second baseman Robinson Cano go to the Mets for a prospect-heavy package. Diaz had starred in Seattle, leading the majors with 57 saves in 2018 -- which tied Bobby Thigpen (1990) for the second most in a single season in baseball history, trailing only Francisco Rodriguez's 62 in 2008.
But his early tenure in New York was anything but successful. In his debut season in the Big Apple, he had a 5.59 ERA (seventh worst among relievers), 15 homers allowed and -0.6 bWAR in 58 innings, as Mets fans routinely booed him while on the mound.
Diaz has righted the ship since, culminating with the dominant 2022. And he's become a fan favorite in New York, with the hit song "Narco," by Australian musician Timmy Trumpet, played at Citi Field every time he exits the bullpen before an appearance.