Dunn grew up in Miami, Florida. He was a running back from 1935 to 1939 serving as team captain in 1935 and 1939 of the Miami Hurricanes football team. In 1938, he played in the first Miami-Florida game, scoring all three touchdowns in a 19-7 Miami win. Dunn set several game, single-season and career UM records for rushing, scoring, and punt returns. Dunn went on to serve as head baseball coach from 1946–54, guiding UM to an 82-73-2 record over his nine seasons. His 1947 club went 11-2, followed by his second-best mark of 14-8 in 1949, playing teams from the state of Florida, military bases and around the Southeast. He died at a Florida hospital in 1980 after a long illness.
In 2009, Dunn was inducted into UM's "Ring of Fame." Dunn's son Gary Dunn, who also played football at UM, represented him at the induction.