Brown, 36, played six seasons in the NFL as a running back for the Cleveland Browns, Tampa Bay Buccaneers, and New York Giants. He retired in 2015 and joined the Bears coaching staff in 2019.
Although Brown has no prior head coaching experience, he is highly respected within the Bears organization. He has worked closely with Nagy and has a good understanding of the team's scheme and personnel.
"Thomas is a bright, passionate coach who has earned the respect of our players," said Bears general manager Ryan Poles. "He brings a wealth of knowledge and experience to this role, and we are confident that he can provide the leadership we need during this transition period."
Brown's immediate task will be to prepare the team for Sunday's game against the Las Vegas Raiders. He will also be responsible for evaluating the coaching staff and making any necessary adjustments.
The Bears are expected to conduct a thorough head coaching search in the offseason. Brown is considered a potential candidate for the permanent role, but he will need to impress during his interim tenure in order to be seriously considered.
"Thomas is a great coach and a great person," said Bears running back David Montgomery. "He knows how to get the best out of us and I'm excited to see what he can do as head coach."
"He's a tough but fair coach," added Bears wide receiver Darnell Mooney. "He's going to demand the best from us, and I'm confident that we can respond and have a strong finish to the season."