The loss ended the Packers' 11-game winning streak on the Bears' home field and extended the Bears' winning streak to eight, their longest since the 1985 Super Bowl season.
"Any time you go that long without beating someone on your home turf, it's huge for us," Bears coach Lovie Smith said of the win. "When someone has beaten you 11 times in a row at home, you don't have to talk about it a lot because a few other people talk about it."
The win loomed even larger because the Minnesota Vikings also won to stay within two games in the NFC North, and the Carolina Panthers kept pace with the Bears' in the chase for a first-round NFC playoff bye - the Bears and Panthers are 9-3 but the Bears own the tiebreaker edge based on their 13-3 win over Carolina.
"We made plays when we had to in the second half, and right at the end of the first half that was great play by Peanut," Bears linebacker Brian Urlacher said. "We sent an all-out blitz, so he's on an island out there and he makes a big play for us."
Tillman's interception wasn't the only turnover forced.
Cornerback Nathan Vasher clinched the win with a fourth-quarter 45-yard interception return and Tillman also forced a fourth-quarter fumble on a blind-side sack of Favre as the top-rated Bears' defense held firm despite yielding more net yards (358) than in any game this season.
"Our defense did not have one of our better games," Bears linebacker Lance Briggs said. "We have a lot to correct."
The Packers owned a 28:42-16:18 time-of-possession edge through three quarters and had 26 first downs to the Bears' 10.
"It was the first time all year I felt early on in the game we were out of character," safety Mike Brown said about the Bears' defense. "We wanted the game so bad I think people were just too excited, too hyped up. The huddle was quite heated. . . . We had to get everyone to calm down a little bit and relax and just let the game come.
"I think as the game progressed we relaxed a little bit and played our game."
The Packers had countered a 21-yard second-quarter Gould field goal by scoring on Samkon Gado's 2-yard touchdown run, the first TD at Soldier Field against the Bears' defense since the Bengals on Sept. 25.
The Bears had come right back with a 49-yard drive to Gould's 40-yard field goal, and trailed 7-6 before Tillman's interception. Favre had dissected their defense with seven completions in eight tries on a 75-yard drive, then the Packers called for a shovel pass to running back Tony Fisher. But Favre couldn't throw the ball with Brown blitzing. He threw it in the end zone to Tillman, who nearly took it all the way in a return similar to Vasher's 108-yard missed field goal return to end the first half two games earlier against San Francisco.
"As soon as I caught it, I knew I was going to run out of the (Bears') end zone because there was only 24 seconds left," Tillman said. "I figured, why not take a chance? I had nothing to lose I gambled right and we got three points out of it.
"It's (running 95 yards) hard. Like, the closer you get to the end zone, the harder it is."
Vasher sealed the victory in the fourth quarter after the Bears had widened their lead to 12-7 on Gould's 35-yard field goal.
Favre, who finished 31-of-58 for 277 yards, threw for wide receiver Donald Driver on the line of scrimmage but the ball went right to Vasher, who made his NFC-leading seventh interception and took it back 45 yards for his second touchdown of the year and the clinching score with 3:06 left in the game.
"Our No. 1 goal defensively is really to score each play and that's what we strive for," Smith said. "From there, we start talking about getting turnovers.
"That's a part of playing good defense. We're supposed to get takeaways and put our offense in good field position. Today, our defense was able to give our offense good field position most of the day."
The offense just did very little with it. Thomas Jones did rush for 93 yards to reach 1,005 for the season and Adrian Peterson ran for 33 yards in the fourth quarter on the 63-yard drive to Gould's fourth field goal.
Yet the offense squandered starting field position at Green Bay's 31 with a Kyle Orton interception in the first quarter, at the Packers' 45 with a second-quarter Jones fumble and failed to score a touchdown despite averaging their own 47 for the starting point of their drives.
Orton went 6-of-17 for 68 yards with a passer rating of 23.7. Wide receiver Muhsin Muhammad went without a catch for the first time in 51 games.
"We've got to find ways to do more in the passing game and just go back to square one and see where we're at," Orton said. "We didn't play very well in the passing game, didn't make enough plays, made a couple when they were there but didn't make enough."
They'd like to put the memory of their 188-yard offensive game in the past, just like they've done with the Packers' streak.
"It's over," wide receiver Bernard Berrian said of the streak. "We put that behind us."