One of the team's most consistent defenders in 2007, when he posted 97 tackles and a remarkable eight forced fumbles, Harris will earn about $3 million per year in so-called "new money" under the terms of the extension, which was signed on Thursday afternoon.
The Panthers also re-signed left tackle Travelle Wharton to a six-year deal Thursday.
Harris, a former Chicago Bears part-time starter, figures to bank about $5.5 million to $6 million in the first two years.
Reserve defensive tackle Damione Lewis also signed a three-year contract Thursday. Lewis agreed to the deal over the weekend in what has already been a busy offseason for the Panthers, who are coming off consecutive non-winning seasons.
"We decided to forgo free agency and stay there because he was real happy," said Albert Elias, Harris' agent. "They made a fair offer."
Elias said Harris' deal is for $13.3 million over the next five years, a total that includes some incentives. Harris will receive a $2 million signing bonus this year and a $1 million roster bonus in 2009.
Under his existing contract, signed with the Bears as a rookie in 2005, the three-year veteran would have been entering the final season of the deal, at a base salary of $927,000, without the extension. Carolina officials, excited by Harris' development in 2007, began pitching an extension to him and his agent late in his first season with the franchise.
Harris, 25, was acquired by the Panthers from the Bears last Aug. 2 for a fifth-round draft pick at an early juncture of camp. Carolina was hit hard by injuries early in training camp last summer and veteran Mike Minter, the leading tackler in franchise history, was forced into retirement by lingering knee problems.
It did not take long for Harris to solidify the interior of the Carolina secondary, where he added a physical presence and started in 15 contests. In addition to his 97 tackles and eight forced fumbles, Harris also had one interception and five passes defensed. He has good size and decent range, is an aggressive tackler and is most effective when playing close to the line of scrimmage.
A former Louisiana-Monroe standout, Harris originally entered the league as a sixth-round selection of the Bears in the 2005 draft. He started in 20 of his 25 appearances with the Bears in 2005-06. But Chicago had a surplus at the safety position last summer and Harris became expendable.
For his career, Harris has 209 tackles, one sack, six interceptions, 18 passes defensed and eight forced fumbles. He has appeared in 40 games, including 35 as a starter.
Len Pasquarelli is a senior NFL writer for ESPN.com. The Associated Press contributed to this report.