Mitchell was born in Havelock, North Carolina. He received an athletic scholarship to attend the University of Florida in Gainesville, Florida, where he ran for the Florida Gators track and field team in National Collegiate Athletic Association (NCAA) and Southeastern Conference (SEC) competition from 1986 to 1989. At Florida, Mitchell was coached by Joe Walker. Mitchell placed fourth in the 100 meters race at the 1988 Summer Olympics and missed a probable gold medal in the 4 x 100 meters relay race, because the American team was disqualified in the early heats, after the baton pass between teammates Calvin Smith and Lee McNeill was completed outside the exchange zone. In 1989, Mitchell won the NCAA championships in 200 meters race, and he was inducted into the University of Florida Athletic Hall of Fame as a "Gator Great" in 2005.