Caldwell, 50, will become the first coordinator hired to new head coach Doug Pederson's staff, and a deal between Caldwell and the Jaguars should be done within the next several days.
The news was first reported by NFL Network.
Caldwell has spent the past 15 years as an assistant coach in the NFL after spending 11 years in the league as a linebacker with the Philadelphia Eagles, Cleveland Browns, Arizona Cardinals, Baltimore Ravens, Carolina Panthers and Chicago Bears. He was drafted in the third round by the Browns in 1993.
Caldwell spent the past three seasons with the Bucs under coordinator Todd Bowles. Caldwell was Bowles' assistant head coach and inside linebackers coach when Bowles was the head coach of the New York Jets 2015-18.
Caldwell has a connection with new Jaguars coach Pederson from their time with the Eagles. Caldwell was a defensive quality control coach and linebackers coach in Philadelphia 2008-12, and Pederson was an offensive quality control coach and quarterbacks coach there 2009-12.
The Jaguars forced a league-low nine turnovers, gave up 27 points per game (28th in the NFL) and allowed 353.1 yards per game (20th) in 2021.