Barkov tweeted Monday night about staying in Florida for six more years.
The extension is worth an average of $5.9 million per season, a source told ESPN's Pierre LeBrun.
"We are thrilled to sign Sasha to a multiyear contract," Panthers general manager Dale Tallon said in a statement. "He is a highly-skilled, intelligent and dynamic young center that plays an exceptional game at both ends of the ice. Sasha is an important part of the foundation of our future and a cornerstone player who is continuing to develop into one of the league's elite centers."
Barkov is third on the Atlantic Division-leading Panthers in scoring, with 12 goals and 18 assists in 38 games this season. The 20-year-old from Finland was drafted second overall by the Panthers in 2013.