He initially attended Oak Hill Academy in Mouth of Wilson, Virginia as a boarding student, where he played on the school's third basketball team.

[3] After graduating from Long Island Lutheran, he opted to enroll at the Perkiomen School in Pennsburg, Pennsylvania for a postgraduate year.

Dunn was rated a four-star recruit and committed to playing college basketball for Virginia over offers from Minnesota, Pittsburgh, South Carolina, Oklahoma State, and Georgetown.

[13] Dunn would make his NBA debut on October 23, recording two points, two rebounds, a steal, and a block in nearly nine minutes of play in the Suns' 116–113 overtime win over the Los Angeles Clippers held in their new home arena, Intuit Dome.

In only his third game played just three days later, Dunn would make his first start for the Suns due to a Bradley Beal injury on his right elbow.