In early January, Anderson was signed to a 10-day contract with the Nets. The fifth-year wing appeared in three games over that span, averaging 1.0 points, 0.7 rebounds and 0.3 blocks across 5.6 minutes. Though he was not given a second 10-day deal, Brooklyn did call upon him later. The Nets ended up short-handed during the restart of the season in Orlando following the COVID-19 hiatus, and in mid-July, Anderson signed a substitution contract with the team. The Virginia product saw a bigger role with the team during bubble play, averaging 3.6 points, 2.7 rebounds and 1.1 assists in 12.9 minutes per contest, which included one start. Facing the Raptors in the postseason, Anderson appeared in three of a possible four games, averaging 6.3 points, 2.7 rebounds and 1.0 assists in 9.4 minutes. Anderson's best performance of the campaign was Aug. 4 in a three-point win over Milwaukee. In that contest, he recorded 11 points (4-7 FG, 3-5 3Pt), four rebounds, one assist and one block in 16 minutes. Ultimately, most of Anderson's 2019-20 campaign was spent in the G League, where he appeared in 31 combined games for the Long Island Nets and Raptors 905. In the G League, he averaged 20.6 points, 6.7 rebounds, 2.6 assists and 1.1 steal. Those numbers led to him being named to the All-NBA G League Third Team.

During the 2018-2019 season, Anderson played in 48 games for the Atlanta Hawks. He made four starts, all near the end of the campaign. Over the last seven games of the season, he averaged 9.6 points. Overall, Anderson averaged 3.7 points and 1.8 rebounds per game. He shot 40.8 percent from the field and 74.3 percent from the free-throw line. The former Virginia Cavalier also shot 31.2 percent from three-point range, which was the second-highest mark of his career. Anderson's season high in points came when he scored 24 points as part of a 136-135 Hawks win over Milwaukee on March 31. In the same game, he pulled down 12 rebounds to set a new career high. Anderson finished the year with 178 total points. He also grabbed 84 rebounds in 463 minutes.

Anderson spent the 2017-18 season as a reserve for the Sixers, coming off the bench in all 38 of his appearances. He averaged 6.2 points per game while continuing to improve his shooting efficiency, as his field-goal percentage ticked up to 43.1 and he shot a career-best 33.0 percent from three-point range. The Virginia product tied his career high in rebounds early on, pulling down 10 in just 16:40 off the bench Nov. 9 against Sacramento. Anderson cleared double-digit points eight times, and he continued his tradition of blowing up during the last game of the regular season with a 25-point effort Apr. 11 against Milwaukee. It was the second-highest-scoring effort of his career, and he also added six rebounds, a steal and a block in that contest. Anderson made appearances in seven of 10 games during the Sixers' two-round postseason run. In Game 3 of the first round against Miami, he scored six points and pulled down four rebounds in just 9:18 on the court.

Anderson's game improved across the board in his second NBA season, as he improved upon his rookie stats in a whole host of categories. He played in 75 games (10 starts) split between the Mavericks and the Sixers in 2016-17, averaging 7.1 points with 3.3 rebounds and 0.5 steals per game. Anderson's shooting percentage rose to 42.4 percent -- almost a two-point improvement -- and his three-point shooting ticked up as well (to 29.9 from 26.5 percent). Anderson cleared double-digit points on 21 occasions. With the Mavs, his season high in scoring was 19 points, set Jan. 22 against the Lakers. He was traded to Philadelphia on Feb. 23 along with Andrew Bogut and a first-round pick for Nelens Noel. Anderson reached the 19-point mark twice in his first six games with the Sixers. He went on to set a new career high with 26 points against the Knicks on Apr. 12, the last game of the season. In that contest, Anderson shot 9-of-11 from the field while rounding out his line with two rebounds, three assists, three steals and a block.

Picked 21st overall by the Mavericks in the 2015 NBA Draft, Anderson went on to appear in 55 games (nine starts) during his rookie campaign. The Virginia product averaged 3.8 points, 2.4 rebounds and 0.5 blocks across 11.8 minutes per game. Anderson also appeared in seven contests for the D League's Texas Legends, where he averaged 23.0 points, 4.6 rebounds and 3.4 assists per game. Back at the NBA level, Anderson scored in double figures for the first time in his career Nov. 10, netting 11 points with two rebounds and an assist off the bench against New Orleans. He went on to score in double figures seven times over the course of the season. From Mar. 25 to 28, Anderson scored 10-plus points in three consecutive games as his playing time ramped up. On Apr. 3 against Minnesota, Anderson narrowly missed a double-double, netting nine points and 10 rebounds. Just five days later, Apr. 8 against the Grizzlies, Anderson successfully collected his first NBA double-double with 19 points, 10 rebounds, three blocks and a steal. He went on to appear in all five playoff games for the Mavs. Anderson contributed double-digit scoring off the bench in Games 3 and 4, then drew the start in Game 5, scoring 14 points with four rebounds, three steals and a block against the Thunder.