Duffner, 49, was employed as defensive coordinator for the Bengals the past two years. A 28-year coaching veteran, Cincinnati's linebackers coach for four years (1997-2000) before being promoted to defensive coordinator in 2001.
Sherman served as offensive line coach (1985-87) and offensive coordinator (1988) at Holy Cross during Duffner's five-year tenure as head coach there (1986-91). Duffner also was head coach for the University of Maryland from 1992-96 where he went 20-35 before moving on to Cincinnati.
"Mark Duffner brings with him a wealth of experience and knowledge of coaching linebackers and defense over the past 28 years," said Sherman in a released statement. "He has a tireless work ethic, a passion for the game and an internal desire to coach here in Green Bay. I have complete confidence he will impact not only our linebackers but our defense and team as well."
The addition of Duffner gives the Packers' current staff eight coaches with experience as an NFL offensive or defensive coordinator (also Mike Sherman, Larry Beightol, Sylvester Croom, Ed Donatell, Tom Rossley, Ray Sherman and Bob Slowik).
Duffner began his coaching career at Ohio State in 1975-76 as a graduate assistant to the legendary Woody Hayes. In 1977, he was named defensive coordinator at the University of Cincinnati, becoming - at age 23 - the youngest defensive coordinator in the Division I ranks.
Duffner played college football at William & Mary, where he was a defensive lineman and was named to the Southern Conference All-Academic team as a senior. He later was inducted into the William & Mary Hall of Fame in 1990.