Yandle agreed to a seven-year contract worth an average of $6.35 million per season, sources told ESPN.
The deal has a no-movement clause for the first six years, a source said.
"We're thrilled. This shows that top players want to win in Florida," co-owner Doug Cifu told The Miami Herald. "Keith wants to win the Stanley Cup in Florida. That's why we were his top priority and vice versa."
Yandle's rights were traded from the New York Rangers to Florida on Monday for a 2016 sixth-round draft pick. The Rangers now also get a 2017 fourth-round pick because Yandle has signed to stay with Florida.
The Panthers had the 23rd-ranked power play this past season and are hoping the 29-year-old Yandle can help improve that.
A four-time All-Star, Yandle had five goals and 42 assists last season for the Rangers. The 6-foot-1, 196-pound defenseman has 65 goals and 246 assists in his 10-year career.
ESPN's Craig Custance contributed to this report.