Kalil's contract is for one year, $8.4 million, a source confirmed. NFL Network first reported the terms of the deal.
That includes a substantial amount in incentives. Kalil made $7.5 million last season with the Panthers.
"He's going to be really helpful for the offense, for the quarterback and for our locker room, bringing in the right kind of guy for us," coach Adam Gase said Friday. "We're fired up."
Kalil, 34, was slated to take his physical Friday at the Jets' facility, but it is unclear when he will start practicing. Gase said the team will wait until Kalil is "good to go" to put him on the field.
The Jets reached out to Kalil a few weeks ago to gauge his interest in coming out of retirement. They believe Kalil's experience will be a help to second-year quarterback Sam Darnold, who still is learning the nuances of Gase's offense.
"I've heard great things," Darnold said. "Obviously, he has done great things in the NFL. He's been an All-Pro, been a Pro Bowler, all that stuff. ... I heard he's a smart dude, so I'm sure he's going to pick it up."
Darnold added: "It's another tool in the toolbox, you could say, to help us win games."
Nick Mangold, who started 11 seasons at center for the Jets before retiring after the 2016 season, tweeted his endorsement of the move. The Jets have largely been unsettled at the position since Mangold retired.
Kalil, a five-time Pro Bowl selection and two-time first-team All-Pro, had retired after the 2018 season following a 12-year run with the Panthers.
This marks the first significant acquisition for general manager Joe Douglas, who was hired in June.
The Jets shopped for a free-agent center in the offseason, showing interest in Matt Paradis, but they opted to stand pat with Jonotthan Harrison. He finished last season after replacing the injured and ineffective Spencer Long.
On Monday, Gase praised Harrison, saying he and Darnold have "a good relationship. They've done a really good job of taking control of the offense and really kind of putting their spin on it. The communication is outstanding between those two."
Harrison has 26 career starts at center, including those with the Indianapolis Colts. Kalil has 145 career starts and was named All-Pro as recently as 2015.