The deal, first reported on Oct. 7, is believed to be worth $39 million, thereby carrying an average annual valuation of $4.875 million.
"Mike is an important part of our team's young core and we are thrilled that he has decided to remain a Panther for the long-term," Tallon said. "He is a dynamic and intelligent defenseman with impeccable character and work ethic. Mike has developed into a difference maker on our blue line and will be an important player and leader for the Panthers for many years to come."
Matheson was drafted 23rd overall by the Panthers in 2012. In 81 games last season, he recorded seven goals, 10 assists, and had an even-strength Corsi rating of 49.7.
So far this season, he's recorded two shots on goal and boasts a Corsi rating of 58.1, while averaging 21:05 through two games.
Matheson has also represented Canada at the past two World Championships, and is clearly seen as a key building block in Florida.