The news came after the All-Star slugger collapsed in pain after swinging at a pitch in the fifth inning of a 3-2 loss to the Arizona Diamondbackson Thursday.
InitialX-rays on the shoulder revealed a dislocation, but follow-up tests showed the tear. Conforto will go on the disabled list Friday, the team said.
"It turns your stomach," manager Terry Collins said after the game. "A player was having a tremendous year and really making a name for himself. To go down like that, and that kind of injury, is tough to watch."
With two outs and runners on first and second, Conforto swung through a 95-mph fastball byRobbie Ray. He collapsed and grabbed his shoulder. Conforto stayed down for about 40 seconds before being helped to his feet by Collins, trainer Ray Ramirez and a member of the coaching staff.
"I can't go out there and predict that," Collins responded when asked if Conforto's season was over. "I'll just let the doctors tell us what's going on."
Brandon Nimmo replaced Conforto and was called out on strikes.
Drafted 10th overall by the Mets in 2014, Conforto is batting .279 with 27 home runs and 68 RBIs this season.
"He's been the heart of this team all year," rookie Dominic Smith said. "He's worked so hard, and for him to get hurt like that is definitely a blow to the team. It's a blow to our spirits and emotionally you feel for him."
Information from The Associated Press was used in this report.
Conforto dislocates shoulder
Mets OF Michael Conforto exits the game after suffering a shoulder injury in the bottom of the fifth.