Dunn signed with the Atlanta Hawks as a free agent in November 2020, but only played nine games for the team due to ankle surgery.

During his junior year in 2010–11, Dunn averaged 26.5 points, 10 rebounds, 5 steals and 5 assists per game to lead the Whalers to a 27–0 record and a victory in the Connecticut Class L State Championship against Northwest Catholic High School.

[4] On December 11, 2013, it was announced Dunn would undergo shoulder surgery and miss the rest of his sophomore season[5] after playing four games.

Dunn was named Big East Player of the Week on January 4, 2016 after scoring 26 points in a win against St. John's and a 26-point outing in a victory over ninth-ranked Butler.

[12] On July 7, he signed his rookie-scale contract with the Timberwolves and joined the team for the 2016 NBA Summer League.

[16] On November 1, he had 10 points, six assists and five steals in his first career start, helping the Timberwolves defeat the Grizzlies 116–80.

In his debut on October 28, in a 101–69 loss to the Oklahoma City Thunder, Dunn came off the bench and had eight points and five fouls, while also aggravating his finger.

[21] On December 9, 2017, he had 17 points, nine assists and seven rebounds and made two free throws with 2.9 seconds left to lift the Bulls to a 104–102 victory over the New York Knicks.

[27] After recording nine points and seven assists on October 22 against the Dallas Mavericks,[27] Dunn was sidelined with a sprained MCL in his left knee.

[28] On December 10, after sitting out nearly seven weeks, Dunn returned to the lineup and finished with nine points in 20 minutes in a 108–89 loss to the Sacramento Kings.

[40] He made his debut for the team the same day, recording two points, five rebounds, three assists and two steals in a 113–122 loss to the Atlanta Hawks.

[44] On February 22, 2023, Dunn signed a 10-day contract with the Utah Jazz, reuniting with Bulls teammate Lauri Markkanen.

[47] On March 24, 2024, Dunn was suspended two games after initiating an altercation and throwing a punch at Houston Rockets forward Jabari Smith Jr.[48] On July 18, 2024, Dunn joined the Los Angeles Clippers in a sign-and-trade agreement in exchange for Russell Westbrook, the draft rights to Balša Koprivica, a second-round pick swap and cash considerations.