Lewis was offensive coordinator for the Packers from 1992-99 and the Minnesota Vikings in 2000-01.
Defensive coordinator Kurt Schottenheimer also will be the defensive backs coach.
Former Michigan State head coach Bobby Williams filled the vacant running backs position Jan. 10.
Detroit has had trouble attracting candidates for its vacant coaching jobs because head coach Marty Mornhinweg has only one year remaining on his current contract. Mornhinweg is 5-27 in his first two seasons with the Lions.