For Harris, it is a return to the place his NFL career started, and he fills a need in the Bears' secondary.
"It's great," Harris said on "The Afternoon Saloon" on ESPN 1000. "The tradition Chicago has is second to none. It's an organization that's been around since the beginning. To play for a team with that tradition feels good.
"It felt great to hold up that George Halas trophy in '07 after we beat the Saints [for the NFC title], so I'm hoping we could take it a step further and hold up the Lombardi Trophy."
Williams is a restricted free agent who hasn't been able to crack the starting lineup because of Pro Bowl linebacker Lance Briggs.
Harris' contract was restructured in the deal, a source told ESPN NFL Insider Adam Schefter. It was trimmed by a year and now ends after the 2011 season. It's worth $3.5 million with a $500,000 roster bonus due on March 5, 2011.
Williams is signed for the 2010 season only.
"Chris is going back to an organization where he has familiarity and we wish him the very best," Panthers general manager Marty Hurney said in a statement. "He has done everything we have asked and has been a valuable member of our team. Right now we have some young safeties who will get the opportunity to continue to earn playing time."
Harris recently informed linebacker Brian Urlacher that he was on his way back to Chicago, according to a team source.
The Bears told Williams on Tuesday that he will be dealt, according to the source, and that he wouldn't be needed at team facilities for voluntary workouts.
The 25-year-old Williams has played in all 16 games in each of the past three seasons with the Bears, and had a career-high 43 tackles last season.
"Jamar is a versatile linebacker who brings experience, athletic ability and can help on special teams as well as compete for time at linebacker," Hurney said.
Harris will be reunited with former Carolina defensive end Julius Peppers, whom the Bears signed in the offseason.
"I think he'll be a great impact," Harris said. "He's an excellent edge rusher. That's one thing he brings is constant pressure."
After two seasons with the Bears, Harris was traded to Carolina in 2007. Harris has made 338 career tackles to go with 10 interceptions, including five in the past three seasons.
Harris was deemed expendable by the Panthers after he struggled some in 2009 and Carolina added depth at safety.
A sixth-round pick of the Bears in 2005, Harris likely will be paired as a starting safety with this year's third-round pick, Major Wright.
A fourth-year veteran, Williams recently signed a one-year, restricted free-agent tender, which opened the door for the trade. Williams spent his entire career with the Bears as a reserve, but started in two games last season, and finished the year with 49 tackles and two pass breakups.
The Bears also announced Tuesday they will not renew the contract of director of college scouting Greg Gabriel.
Information from ESPN.com's John Clayton and ESPNChicago.com's Jeff Dickerson and Michael Wright, and The Associated Press was used in this report.