Shortly after his playing career ended, Dunbar started coaching at the high school level, first at Opelousas Senior High School in Opelousas, Louisiana in 1996, before moving to Beau Chene High School in Arnaudville, Louisiana in 1997. Dunbar returned to college football in 1998 and 1999 at Division I-AANicholls State University as the defensive line coach. In 2000, he returned to his alma mater, LSU as a member of the strength and conditioning program through 2002. In 2003, he was hired as defensive line coach by Oklahoma State'sLes Miles and remained in that role through 2003. While at Oklahoma State, Dunbar tutored Kevin Williams during his breakout senior season and helped him become the first Cowboys defensive lineman to be a 1st-round draft pick since Leslie O'Neal17 years earlier. In 2004, Dunbar moved to the NFL after being hired by Lovie Smith to coach the Chicago Bears defensive line. He helped tutor a young and talented line that included rookie 1st-round pick Tommie Harris and 2nd-rounder Tank Johnson. The Bears led the NFL in 3rd-down defense, allowing opponents to convert at a 30.5% rate while ranking 15th in the NFL in pass defense. In 2005, Dunbar returned to his alma mater, LSU, which had just hired Les Miles as their new head coach. During the 2005 season, Dunbar’s linemen paved the way for the Tigers defense to rank #5 in the nation in total defense at 276.8 yards per game and 7th in the country in rushing defense at 94.8 yards per game. The defense also allowed only 15.2 points per game, which ranked 8th in the nation, and led the SEC with 39 team sacks. In 2006, Dunbar returned to the NFL and was hired by the Minnesota Vikings new head coach, Brad Childress. Under his tutelage, the so-called "Williams Wall", consisting of defensive tackle Kevin Williams and nose tacklePat Williams, led the NFL in defense against the run each year between 2006 and 2008. Over the same period, the Vikings only allowed an average of 70.8 rushing yards per game. He remained with the Vikings through the 2011 season. The New York Jets hired Dunbar on February 13, 2012 to serve as their defensive line coach which he did from 2012 to 2014. In January 2015, Dunbar was hired as defensive line coach for the Buffalo Bills for the 2015 season, but was fired on March 13, 2016 by head coach Rex Ryan after only one season. In May 2016, he was hired as defensive line coach at the University of Alabama under head coach Nick Saban. Dunbar remained in that role for two seasons through 2017. On February 8, 2018, Dunbar was named defensive line coach of the Pittsburgh Steelers.