After having a bad experience playing ninth grade football, Dawson chose not to go out for his high school team his sophomore year. He joined the football team as a junior after being recruited due to his size by the school's football coach. He was an all-state offensive tackle in high school and eventually accepted a football scholarship to attend the University of Kentucky. Among his high school teammates were future NFL players Marc Logan and Cornell Burbage.
Dawson was selected by the Pittsburgh Steelers in the second round of the 1988 NFL Draft. In his rookie season he played guard alongside Hall of FamecenterMike Webster. When Webster left the team following that season, Dawson succeeded him as the startingcenter. He soon became one of the most respected players among the Steelers, and one of the best in the league at his position. He earned the name "Dirt" for the way he would try to grind defenders into the ground. In contrast, his friendly off-field demeanor led to a second nickname, Ned Flanders, after the annoyingly cheerful character from The Simpsons.
"To me he was the best athlete to ever play that position. He was very powerful and explosive, just a rare combination of quickness, explosion, and he was a very dependable player. This guy hardly ever missed a game. He redefined the position."
Dawson was named to seven straight Pro Bowls from 1992 to 1998 and was a six-time AP First Team All-Pro. In 1993, he was named co-AFC Offensive Lineman of the Year by the NFLPA and in 1996 he was named the NFL Alumni’s Offensive Lineman of the Year. He played in 170 consecutive games, the second most in Steelers history, until severe hamstring injuries forced him to sit out nine games in 1999 and seven more games in 2000. Dawson was released by the Steelers following the 2000 season partly due to these injuries and partly due to salary cap reasons. He opted to retire rather than trying to play for another team.
"He was one of the best players that we have ever played against at that position. He had exceptional quickness; I think that really the measure of a center is his ability to play against powerful guys that are lined up over him and try to bull-rush the pocket and collapse it in the middle so that the quarterback can't step up. Dawson had great leverage and quickness with his hands and his feet where he did a great job of keeping that pocket clean for [Neil] O'Donnell and those guys who played behind him."
He is the only player to have played in the two most lopsided games in the Browns–Steelers rivalry, getting his first career start at center in the Steelers 51-0 loss to the Cleveland Browns at home (still the worst loss for the Steelers in franchise history), but was victorious in the Steelers 43-0 win against the Browns in Cleveland ten years later, in the Browns' first game in four years.
Dawson is married (Regina) and has two children. He returned to Lexington after his retirement, where he spent several years as a real estate developer. He filed for Chapter 7 bankruptcy protection in 2010 listing over $69 million in liabilities against just under $1.5 million in assets. He currently resides in San Diego, California, where he is a sales executive for a promotional products company.
In 2001 Dawson and his wife established the Dermontti F. and Regina M. Dawson Endowed Graduate Fellowship in Education scholarship at his alma mater, the University of Kentucky (UK). Dawson was appointed to the school's board of trustees by Kentucky governor Ernie Fletcher in 2005. He is a member of UK's College of Education’s "Alumni Hall of Fame" and the UK Hall of Distinguished Alumni as well as a charter member of the UK Athletics Hall of Fame. In addition, his jersey has been retired by the school.