Stewart's extension, which runs through the 2017 season, is worth $36.5 million with $22.5 million guaranteed, a source with knowledge of the situation told NFL.com and NFL Network's Albert Breer. Stewart had been in the final year of his contract.
Stewart told The Associated Press it was a relief and a blessing to receive a new deal, and he's excited that he and backfield mate DeAngelo Williams, who refer to themselves as "Double Trouble," will remain together.
"We have a group of guys that understand the team aspect of winning football games," Stewart, the Panthers' first-round draft pick (13th overall) in 2008, said after Saturday night's game. "That is ultimately what I want to do. I want to be on a good team, and this is a good team. We got a lot of good guys. The offensive line, Ryan Kalil, Jordan Gross... all over the team we got a lot of good guys. There is no other place that I would rather be."
Stewart, who's entering his fifth NFL season, rushed for 761 yards and four touchdowns in 2011. He ran for a career-high 1,133 yards and 10 touchdowns in 2009.
Since Stewart's first season in 2008, the Panthers have rushed for 9,189 yards, the most in the NFL during that span.
The Associated Press contributed to this report.