"After spending a lot of time this spring thinking about my NFL future, I have made a decision to retire," Urlacher said in a statement he posted on Twitter. "Although I could continue playing, I'm not sure I would bring a level of performance or passion that's up to my standards. When considering this along with the fact I could retire after a 13-year career wearing only one jersey for such a storied franchise, my decision became pretty clear."
The Bears parted ways with Urlacher after last season when the two sides couldn't agree on a new contract. Urlacher became a free agent and had said he still had some football left, but chose to retire after briefly testing the free-agent market.
"I want to thank all of the people in my life that have helped me along the way," Urlacher said. "I will miss my teammates, my coaches and the great Bears fans. I'm proud to say that I gave all of you everything I had every time I took the field. I will miss this great game, but I leave it with no regret."
Urlacher told "The Waddle & Silvy Show" on ESPN 1000 that he's happy with his decision and will be filling out his retirement papers in the immediate future.
"I made my mind up a long time ago," Urlacher said. "It wasn't like an overnight decision. But I feel great about it. It's nice to have it behind me now and go onto the next stage of my life, whatever that may be. I thought it was time.
"I didn't want to put another jersey on for any other team. Obviously, it wasn't going to be for the Bears this year, so I thought it was the right thing to do to shut it down."
Urlacher enjoyed a very close relationship with former coach Lovie Smith, who was fired after last season and replaced by Marc Trestman. He was asked if he thought he'd still be with the Bears if Smith were still the coach.
"One-hundred percent, I think so," he said. "My want-to would be there more, as well. I think my desire to want to play for the Bears and still be there with his staff and my teammates would be a lot more as well. I love playing for him. He made football fun. He made our locker room fun. Our meetings were a blast, and everyone looked forward to going to work, every day."
A call to Smith was not immediately returned.
Urlacher never visited teams as a free agent. He discussed contract parameters with some teams that were interested, but there were never serious negotiations, a source told ESPN NFL Insider Ed Werder.
"We talked to every team in the NFL, and maybe in July or August it would have happened, but I'm not going to wait," Urlacher said. "I want to be somewhere where somebody wants me. I don't want to go somewhere where, 'Oh, so-and-so got hurt, we need you.' I don't want that to be the situation.
"The Bears offered me the contract they offered me and that was probably the best contract I was going to get from anywhere. And I'm not going to put my body through what it goes through for what the offer was."
While he left the Bears angry and vowed he had more football in him, Urlacher continued to work out in Arizona but gradually came to enjoy his free time, the source said. Those close to Urlacher think his primary motivation to play again was the result of not wanting his career to end with a subpar 2012 season.
Former Bears coach Mike Ditka said he was golfing at the same club as Urlacher on Tuesday, when Urlacher hinted at retirement.
"I asked him what he was going to do and he wasn't sure, but he said, 'I think I'm going to hang them up, 13 years, it's been a long time,'" Ditka said on "The Carmen & Jurko Show" on ESPN Chicago 1000. "And basically, that's what he said.
"I want to say one thing: He looked like he could play football for another 10 years. He was in great shape, great attitude about it, very respectful to the fact he spent 13 years with one club, with the Chicago Bears. He's a certain Hall of Famer in my opinion. He doesn't have to apologize to anybody for the way he played the game."
Bears linebacker Lance Briggs played 10 seasons alongside Urlacher, and he told "The Carmen & Jurko Show" on Wednesday that the emotions involved prevented him from expressing his feelings.
"Here is the thing: I don't have words in regards to Brian right now," he said. "He meant something different for me than he did for most. So for most, it's just a thankful answer. For me, it's deeper than that. I'm just not ready to speak on it."
Jerry Angelo was the Bears' general manager from 2001 through the 2011 season and said Urlacher won't be forgotten.
"He did the right thing for himself and his fans," Angelo said. "A Hall of Fame player and teammate. He not only made the Bears better, he made football better. Not many can say that. He'll be missed, but never forgotten."
The ninth overall pick in 2000, Urlacher was named NFL defensive rookie of the year after posting 123 tackles, eight sacks and going on a five-game sack streak, the third-longest rookie streak in NFL history and tied for the longest rookie streak in Bears history. He was the NFL defensive player of the year in 2005 and an eight-time Pro Bowler.
Urlacher finished his final season having contributed 68 tackles and an interception returned 46 yards for a touchdown on Nov. 4 against the Tennessee Titans. Urlacher's 180 starts rank No. 3 in franchise history.
A sprained MCL in the 2011 season finale at Minnesota played at least a small role in Urlacher's value diminishing to the Bears. Urlacher injured his left knee when he collided with teammate Major Wright in the end zone during the fourth quarter against the Vikings.
It was believed initially that surgery wouldn't be required on the injured knee. But after participating in the first few workouts of training camp in 2012, Urlacher underwent an arthroscopic debridement procedure on the knee, which kept him out of the entire preseason. Urlacher returned to practice on Sept. 3 and played in the Sept. 9 opener against the Indianapolis Colts.
Throughout the season, the Bears kept Urlacher on a limited practice schedule, and that contributed to the linebacker struggling to regain form.
Urlacher put together a nine-tackle performance in Week 13 against the Seahawks, but he suffered a hamstring injury while chasing down quarterback Russell Wilson during a 23-17 loss in overtime, which ended his 2012 season with four games remaining. Before that, Urlacher had played in every game in the two previous years after missing 15 games in 2009 due to a broken wrist.
"My knee feels great, finally," Urlacher said. "This is the first I got to work out and not just do rehab. ... But I can look at myself in the mirror and say 'There's no way I'll be the player I used to be, or what I think I need to be out there.' Mentally? Yeah, I have it. But physically, I'm not what I used to be. There's no doubt about that. My knee is never going to be the same. I saw that last year, even when I started getting better. I'll never be able to move like I want to. ... I can't do what I want to do and it's frustrating."
Urlacher became a free agent in March for the first time in his career. Although Urlacher engaged briefly in negotiations on a new contract with the team, which indicated a desire to bring him back for a 14th season, the sides cut off talks on March 20, with the Bears issuing a statement announcing the sides couldn't come to agreement.
On April 16, Bears general manager Phil Emery said he harbored "absolutely" no regrets for how the team handled the failed negotiations. The club's best and final offer to Urlacher was a one-year contract that maxed out at $2 million.
"It was a very straightforward process," Emery said. "We had a very honest and open exchange between Brian and his representatives, his agents. There was no lack of clarity. There were no surprises during this period.
"You know Brian has been a great player. He's a Hall of Fame player. He's done great things for the Chicago Bears. It's been a win-win as far as Brian and the Chicago Bears. That's been a great [relationship] for the city of Chicago, for our fans and for the Bears. It's also been good for Brian. We've committed more resources to Brian than any Bears [player] in the history of the organization. We were willing to commit more. In the end, we just could not agree on what that amount was. It's no more than that."
Two days after negotiations between Urlacher and the team ended, the linebacker told "The Waddle & Silvy Show" on ESPN 1000 he would have appreciated at least a phone call from the Bears before the team sent out a news release to announce the sides had shut down talks.
"I would have appreciated a call from, maybe not Phil, but [team chairman] George [McCaskey] or somebody else I've been around," Urlacher said. "I haven't been around Phil. He's been here for one year, so I don't know him all that well, but [a call] from somebody else in the organization I've been around for a long time [would have been appreciated]."
McCaskey spoke with Urlacher later and in April mentioned the team had not officially ruled out a possible return for the linebacker. Emery also recently said "never to say never" when asked about Urlacher but also indicated it was highly unlikely the linebacker would play for the Bears in 2013.
That likelihood decreased even more toward the end of April, when the team used two draft picks to select Jonathan Bostic and Khaseem Greene.
McCaskey released a statement Wednesday in which he said: "How lucky we were that Brian Urlacher was a Chicago Bear.
"Brian announced his retirement in the same, understated way in which he carried himself at Halas Hall the last 13 years -- he simply wanted to be one of the guys and play the game he loves. But his rare ability, work ethic and passion for football put him among the greats to ever play the game. Besides superlative play on the field, he was also the unquestioned leader in the locker room, as well as the sometimes reluctant face of the franchise. Brian is a special person who represented our team and our city with skill and humility while never seeking acclaim or recognition."
Briggs said Tuesday that the defense was "very different" during organized team activities without Urlacher manning the middle linebacker spot.
"I didn't call plays before, and now I'm calling the plays," Briggs said. "I just have a lot of respect [for the job Urlacher did]. I've been spoiled for the last 10 years."
Briggs abruptly ended the interview session when asked whether he was surprised that Urlacher remained unsigned, an indication he likely knew about his former teammate's pending announcement.
ESPN NFL Insider Ed Werder contributed to this report.