The Panthers sent a sixth-round pick in Friday's NHL draft to the New York Rangers for the rights to the veteran defenseman, whose contract expires on July 1.
Florida was working on a contract Monday night with Yandle, who made $5.25 million this past season and was 15th among defensemen with 47 points.
Yandle has had three 50-point seasons in his career; the Panthers, in their entire history, have had two defensemen reach that total in a season.
"We wouldn't have made the trade if we weren't confident that we could come to a conclusion and get him into our system," Panthers general manager Tom Rowe said Monday night.
The Rangers said they would also receive a fourth-round pick in the 2017 draft if Yandle signs with the Panthers, who won the Atlantic Division title this past season and are expected to be a big player in free agency.
"I think it's a sign to the fan base that we're real serious about winning the Stanley Cup," Rowe said. "We want to build off the momentum that started with last year and continue growing. And we want the players to also know that we're real serious about winning and we want to be a consistent playoff team."
New York acquired Yandle in March 2015 from Arizona along with another defenseman, Chris Summers, and a fourth-round selection. The Rangers gave up top prospect Anthony Duclair and a conditional first-round draft pick. Yandle had 58 points (seven goals, 51 assists) in 103 games with New York over parts of two seasons.
Yandle spent nearly nine seasons with the Coyotes before the trade to the Rangers.
The Panthers were looking to add a defenseman after trading Erik Gudbranson to the Vancouver Canucks last month. Florida is also in talks with defenseman Brian Campbell, who has been with the team for the past five seasons and is likely to become a free agent.
"I believe that's the avenue he's going to take," Rowe said. "We had to go with the next phase of our plan and we felt Keith was a real good target to go after."
Rowe was asked if Yandle may be Campbell's replacement.
"Yeah, possibly," Rowe said. "We're just looking to ice the best possible team that we can."