Mann attended and played college football at the University of Nevada, where he played defensive end from 1979 to 1982. During his senior season, he led the Big Sky Conference with 14 sacks and was named the conference's Most Valuable Defensive Lineman. In 2015, he earned his bachelor's degree in business administration from Strayer University. Two years later, June 24, 2017, he received an MBA from Strayer University.
Mann finished his career with the Redskins with 82 sacks, second-most in franchise history, and 17 forced fumbles, the most in franchise history, and also won Super Bowl XXII and Super Bowl XXVI. He was released by the Redskins and signed as a free agent with the San Francisco 49ers in 1994, where he won another Super Bowl (Super Bowl XXIX) before retiring.
Mann helped found the Good Samaritan Foundation with his Washington teammates Art Monk, Tim Johnson and Earnest Byner. The foundation provides youth with the environment needed to equip them with the skills, training and resources necessary to compete successfully in society through the Student Training Opportunity Program (STOP). The program serves more than 50 high school students, four days a week during the school year and five days a week during the summer providing after-school programs, tutoring and mentoring.
In 1993, Mann was voted the "Washingtonian of the Year."  Among his many accomplishments, Mann serves as a member of the board of Inova Health Systems and as Chairman of the Inova Alexandria Hospital Quality Committee, the board of the McLean School and a Deacon with Grace Covenant Church in Chantilly, Virginia. He also serves on the Honorary Board of Directors for Easter Seals Serving DC|MD|VA, located in Silver Spring, MD.