Phillips replaces former defensive coordinator Frank Bush, who was let go along with three other coaches in a house-cleaning that spared head Coach Gary Kubiak, who will return for a sixth season.
Phillips has worked with Kubiak before when their tenures overlapped with the Denver Broncos from 1989-91. Kubiak is a former Broncos player and Phillips was Denver's defensive coordinator from 1989-92 and its head coach from 1993-94.
Phillips, 63, was dismissed by the Cowboys in November after a 1-7 start. He racked up a 34-22 career mark running the Cowboys, winning the NFC East twice.
In all he boasts 35 years of coaching experience -- 20 of them as defensive coordinator for the Saints, Eagles, Broncos, Falcons and Chargers.