New York and deGrom agreed on a $7.4 million pact, a sharp raise from the $4.05 million he made in 2017 when he went 15-10 with a 3.53 ERA and a career-best 239 strikeouts.
Harvey's deal is worth $5.625 million and Syndergaard's agreement is for $2.975 million, nearly five times more than the $605,500 he made in 2017.
Harvey, who was reportedly on the trade block in December, posted a 5-7 record and career-worst 6.70 ERA last season in 19 starts. He averaged a career-low 6.5 strikeouts per nine innings in 2017.
Injuries have been a bugaboo for Harvey since missing the entire 2014 season for Tommy John surgery, replacing the ulnar collateral ligament in his right elbow. He required thoracic surgery on his right shoulder in 2016 and shoulder and hamstring injuries sent him to the disabled list in 2017.
Harvey, 28, has a career record of 34-35 with a 3.51 ERA. deGrom, 29, is 45-32 with a 2.98 ERA in four big-league seasons and Syndergaard is 24-18 with a 2.89 ERA in parts of three seasons.
The 25-year-old Syndergaard was just 1-2 with a 2.97 ERA in seven starts last season. He missed most of the season due to a partially torn right lat muscle.
The Mets also reportedly agreed to terms with right-handed reliever Jeurys Familia ($7.925 million), catcher Travis d'Arnaud ($3.475 million) and shortstop Wilmer Flores ($3.4 million).
--Field Level Media