The hiring of Monte Kiffin, 72, comes three days after the Cowboys fired defensive coordinator Rob Ryan.
Dallas was 14th in the NFL in yards allowed and 24th in points allowed in an 8-8 season.
Monte Kiffin spent the last four seasons as defensive coordinator for the Tennessee Volunteers and then USC but has extensive NFL experience, including guiding the defenses at Minnesota, New Orleans and, for 13 seasons, Tampa Bay. The Buccaneers won Super Bowl XXXVII while Monte Kiffin was on the staff.
He was head coach at North Carolina State from 1980-82, going a combined 16-17.
Dallas had been working from a 3-4 formation under Ryan but Monte Kiffin is known to favor the 4-3 alignment.