Lett, who won three Super Bowl titles over 10 seasons with the Cowboys, will assist defensive line coach Brian Baker during training camp.
"This is just a great opportunity to get some more experience and learn from some of the best coaches in the league," Lett said Wednesday. "When Coach (Jason) Garrett called me, I was excited. It's been so long since I was a rookie and going to the Cowboys now makes it seem like I'm a rookie again. I'm just grateful to return."
Lett is known for being a strong presence along the defensive line and for two crazy plays in his NFL career.
On a Thanksgiving Day game in 1993, Lett touched a live football after a blocked field-goal attempt and the Miami Dolphins recovered and went on to win. In the Cowboys' XXVII Super Bowl victory over the Buffalo Bills, Lett, after recovering a fumble, was stripped of the ball while holding it out in a premature celebration as he was running toward the end zone.
Lett was also suspended three times for violating the NFL's drug policy.
He earned his degree in sociology in 2009 from UNLV where he was a volunteer assistant coach. Last year, Lett was the defensive line coach at UL Monroe, where he expects to return for the 2011 season.
"I just want to help the guys become better people and players," Lett said. "My door is always open to them. I know I've made my mistakes in the past and learned from them, and I want to be a positive influence."
Calvin Watkins covers the Cowboys for ESPNDallas.com.