In his first year in college, Mason appeared in 31 games for the Bulldogs with per-game averages of 6.2 points, 2.2 rebounds and 1.6 assists, earning him the John C. Cobb Outstanding Freshman Award.
His sophomore campaign in 2015-16 was his breakout year. Mason took home All-Ivy League First Team honors,[3] along with a NABC District 13 Second Team selection.[4] He was also recognized with the Bill Madden Toughness Award and was the co-recipient of the Dutch Arnold Most Valuable Player Award (alongside his teammate Justin Sears).[5] Mason emerged as Yale's leading scorer (16.0 points per game) and assist man (3.8 per game),[6] while guiding the Bulldogs to their first ever NCAA Tournament victory, hitting on 9-of-18 from the field and netting a career-high 31 points in Yale's 79-75 upset win over heavily favored Baylor.[7] Yale fell short to Duke in the second round.[8] Mason declared for the 2016 NBA draft, but later withdrew his name.[9]
On November 8, 2016, it was announced that Mason would miss the entire 2016–17 College Basketball season with a broken right foot.[10] He suffered a stress fracture in his left foot in November 2017.[11]
In 2018, Mason transferred to Baylor University to complete his basketball eligibility as a graduate student for the 2018–19 season.[12] Despite dealing with injuries, Mason averaged 14.9 points and 3.4 assists per game in his only season at Baylor.[13]
Professional career
After going undrafted in the 2019 NBA draft, Mason signed his first professional contract with Alba Berlin of the Basketball Bundesliga.[14] He averaged 3.9 points and 0.8 assists per game. On July 3, 2020, Mason left the German team in order to join Liga ACB club Manresa.[15]
International career
Mason has dual citizenship in the United States and Germany, his mother was born in Mainz, Germany.[16] In 2016, Mason was selected for the German national basketball team, to play in the qualification rounds for the EuroBasket 2017.[17][18] He played his first official game for Team Germany on July 30 against Ukraine.[19]