Tom Pelissero of NFL.com reported the team's decision Saturday.
The move will allow Trubisky to become an unrestricted free agent after next season. His long-term future with the organization has been an ongoing question since the end of the 2019 campaign.
ESPN's Adam Schefter reported on April 25 that people around the league felt the Bears would pass on the option that would cost them around $24 million in 2021.
Trubisky looked like he was going to be a long-term starter for the Bears after the 2018 season. The North Carolina alum ranked third among all starting quarterbacks in QBR (71.0), completed 66.6 percent of his passes for 3,223 yards and 24 touchdowns to help the team win the NFC North.
"It's been a focus for us," general manager Ryan Pace told reporters about giving the team options at quarterback. "With the addition of Nick Foles, it's exactly what we talked about from the start. We've increased competition at a critical position and we talked to both players, and the way we view this is it's an open competition. And credit to both those guys for embracing it."
In addition to Trubisky's on-field struggles last season, the financial component of keeping him under contract at a high price in 2021 would have created salary-cap problems.
The combined cap hit for Foles and Trubisky in 2021 would have been around $29.3 million.
Chicago has given itself the ability to evaluate Trubisky for one more year. If he plays closer to his 2018 form, Pace will be happy to re-sign him. If he repeats his 2019 performance, the Bears can move on with Foles still under contract.