Nunn appeared in 56 games (44 starts) for the Heat during the 2020-21 season. In 29.5 minutes per game, he averaged 14.6 points, a career-high 3.2 rebounds and 2.6 assists. He also shot career highs in field-goal percentage (48.5), three-point percentage (38.1) and free-throw percentage (93.3). In a win over the Raptors on Jan. 20, Nunn grabbed a season-high eight rebounds. In a win over the Rockets on Feb. 11, Nunn secured a season-high four steals. In a victory over the Thunder on Feb. 22, the guard handed out a season-high nine assists. On April 19, in a win over the Rockets, he hit a season-high six three-pointers. Against the Bucks on May 15, Nunn scored a season-high 31 points. Nunn appeared in all four playoff games against the Bucks. In 23.3 minutes, he averaged 10.3 points, 1.5 rebounds and 1.5 assists. His best playoff effort was Game 4. In 28 minutes, he recorded 18 points, one rebounds, one assist and one steal with no turnovers.2019
Following three collegiate seasons at Illinois and one at Oakland, Nunn went unselected in the 2018 NBA Draft. He spent the 2018-19 season in the G League with the Santa Cruz Warriors, averaging 19.3 points, 3.8 rebounds, 2.8 assists and 1.4 steals. In April of 2019, Nunn signed a contract with the Heat. He made his NBA rookie debut Oct. 23 in a win over the Grizzlies, totaling 24 points, three assists, two rebounds and two steals in 27 minutes. During a win over the Hawks on Dec. 10, Nunn scored a career-high 36 points, adding six rebounds, four assists and one steal. Less than a month later, in a win over the Raptors on Jan. 2, the guard set a personal best with nine assists. On Mar. 2 against the Bucks, Nunn grabbed a career-high eight rebounds, adding 13 points, two assists and a steal. Against the Raptors on Aug. 3, Nunn blocked a career-high two shots. Eleven days later against the Pacers, the rookie swiped a career-high three steals while also providing 23 points, four assists, two rebounds and a block. For his performances during the regular season, he was named to the All-Rookie First Team. During the first three rounds of the playoffs against the Pacers, Bucks and Celtics, Nunn averaged 3.2 points, 1.2 rebounds and 1.0 assists. In the NBA Finals against the Lakers, Nunn stepped up his game, averaging 10.5 points, 3.5 rebounds and 1.8 assists. Nunn's best playoff performance was Game 1 against the Lakers, when he recorded 18 points, five rebounds and two assists with no turnovers in 20 minutes.