Following four years at Kansas, Mason was selected by the Kings with the 34th overall pick in the 2017 NBA Draft. He proceeded to appear in 52 games (two starts), averaging 7.9 points, 2.8 assists and 2.5 rebounds in 18.9 minutes. Mason shot 37.9 percent from the field, 36.0 percent from three and 81.7 percent from the charity stripe. His 22.7 percent assist rate was the second highest on the Kings. Mason also held the second-best plus-minus per 100 possessions (plus-7.9) on the team. Arguably his best game of the season occurred Mar. 7 during a 13-point loss to the Pelicans. In 29 minutes, Mason posted 16 points (5-10 FG, 1-2 3Pt, 5-6 FT), six assists, one rebound, one steal and one block without a turnover. That was one of his 15 outings with double-digit points and one of his 10 outings with at least five assists. Mason saw the most run in March, and in his 16 appearances that month, he averaged 9.7 points, 3.6 rebounds, 3.0 assists and just over one steal in 21.3 minutes. Under head coach Dave Joerger, the Kings finished 27-55 and did not make the postseason.2018
The 2018-19 season marked Mason's second in the league. He appeared in 38 games for the Kings, seeing 11.4 minutes per game. He averaged 5.1 points, 2.2 assists and 1.1 rebounds. He shot 42.0 percent from the field, 21.9 percent from three and 68.4 percent from the charity stripe. In the six games that he saw at least 20 minutes, he averaged 11.0 points, 5.3 assists and 2.7 rebounds with eight combined steals and a block. During a 20-point loss to the Pelicans on Oct. 19, Mason had his best performance of the season. He posted 18 points (7-13 FG, 1-2 3Pt, 3-4 FT), six assists, one rebound and one steal in 21 minutes. The 18 points represented a career high. His season highs were, respectively, seven assists, five rebounds, two steals, two three-pointers and one block. The Kings finished the year 39-43.
June 22, 2017Drafted by the Sacramento Kings in the second round (34th pick) of the 2017 NBA Draft.
July 13, 2017Signed a contract with the Sacramento Kings
July 4, 2019Waived by the Sacramento Kings.
July 26, 2019Signed a two-way contract with the Milwaukee Bucks