The team made the announcement Monday on Twitter.
Caldwell last was the head coach of the Detroit Lions from 2014 through 2017. His teams had a 36-28 record during his time in Detroit but lost the only two playoff games they made.
Caldwell, 65, also coached the Indianapolis Colts from 2009 to 2011. Under his tutelage, the Colts advanced to the Super Bowl but lost to the Saints in the 2009 season. Caldwell left Indy after compiling a 2-14 record in 2011.
Romeo Crennell is currently serving as Houston's interim head coach after the team moved on from Bill O'Brien in the middle of a disastrous 2020 season.