Pees, who had been the Pats' linebackers coach the last two seasons, replaces Eric Mangini, who was named coach of the New York Jets earlier in the day.
"Dean Pees has done an outstanding job coaching our linebackers," said New England Coach Bill Belichick. "When he joined us, Dean brought a wealth of experience into this system and has been a significant part of our success over the past two seasons."
Pees, 56, has 33 years of coaching experience, including 15 seasons as a defensive coordinator and six years as a head coach at the collegiate level. In Pees' first year as the Patriots' linebackers coach, they ranked ninth overall and sixth in the league against the run.
Pees spent six seasons as the head coach at Kent State (1998-03). From 1995-97, he was defensive coordinator and linebackers coach at Michigan State.