The offer averaged $14 million per year and effectively guaranteed the four-year veteran $29 million at signing, sources told ESPN NFL Insider Adam Schefter.
"Happy to be back in Chicago," Fuller said during a conference call. "It was a crazy process, but I'm glad it's all over."
The Bears placed the transition tag on Fuller on March 6, guaranteeing the cornerback $12.971 million for 2018 and giving Chicago the right to match any offers.
"It was crazy not knowing what to expect," Fuller said. "I never would have expected it, but when [the Packers offer] came, it was something to consider from the business side of it. I think at the end of the day, how it all played out, I'm definitely happy and just looking forward to [being back in Chicago]."
Fuller, the Bears' 2014 first-round draft pick, looked all but done in Chicago before the start of the regular season after he missed the entire 2016 campaign due to a routine knee scope.
The Bears declined his fifth-year option and brought in multiple cornerbacks last spring, in essence to replace Fuller, but the 25-year-old defensive back had arguably his best season with 67 tackles, two interceptions and 22 pass breakups.
"We could not be happier to have Kyle under contract for four more years," Bears general manager Ryan Pace said in a statement. "We feel he is an ascending player on our top-10 defense and we look forward to him having many more productive seasons here in Chicago."
Fuller has started 46 games for the Bears. As a rookie in 2014, Fuller was named NFC Defensive Player of the Week for his two-interception performance against San Francisco in Week 2.
Chicago also brought back starting cornerback Prince Amukamara in free agency. Amukamara's new deal is for three years and $27 million with $18 million fully guaranteed.