He played college basketball for two seasons with Tulsa before transferring to Missouri, where he earned second-team all-conference honors in the Southeastern Conference (SEC).

After forgoing his senior year in college to enter the 2014 NBA draft, Clarkson was selected by the Washington Wizards in the second round with the 46th overall pick and was immediately traded to the Los Angeles Lakers.

As a junior, he averaged 20 points, six rebounds and four assists per game, leading his team to a 32–8 record and the Class 5A state semi-finals.

[11] On November 11, 2009, Clarkson signed a National Letter of Intent to play college basketball at the University of Tulsa.

[12] As a senior, he averaged 18.9 points, 6.1 rebounds, 3.4 assists, and 2.1 steals, leading his team to a 38–2 record and a semi-final loss in the state championship.

He was also named to the Wooden Award Midseason Top 25 list in January 2014 and won three Southeastern Conference Player of the Week honors.

He was later traded to the Los Angeles Lakers on draft night for cash considerations,[16][17] and joined the team for the 2014 NBA Summer League.

[24] Clarkson after joining the Lakers garnered a huge following in the Philippines owing to his Filipino heritage and the existing fanbase of the NBA team in the country.

[28][29] In the Lakers' season opener on October 26, 2016, Clarkson scored a team-high 25 points off the bench in a 120–114 win over the Houston Rockets.

[35] On February 8, 2018, Clarkson was traded, along with Larry Nance Jr., to the Cleveland Cavaliers in exchange for Isaiah Thomas, Channing Frye and a 2018 first-round draft pick.

[39] On December 24, 2019, Clarkson was traded to the Utah Jazz in exchange for Dante Exum and two future second-round draft picks.

He won the NBA Sixth Man of the Year Award over Jazz teammate Joe Ingles, who was the runner-up.

[47] On December 15, 2022, Clarkson led the Jazz to a 132–129 overtime victory over the New Orleans Pelicans with a game-leading 39 points and 8 rebounds.

[54] However, Clarkson did not meet the FIBA eligibility requirements to be considered a Filipino citizen as he acquired his Philippine passport after age 16.

[55] Clarkson visited the Philippines in August 2015 on the invitation of Manny Pangilinan, the then-president of Samahang Basketbol ng Pilipinas (SBP), the national basketball federation of the Philippines, to observe the training of Gilas, aside from fulfilling his commitments as an endorser of Smart Communications, which was also presided by Pangilinan.

[64] Clarkson managed to get his first win with the national team, defeating Japan 113–80, in which he recorded 22 points, six rebounds and nine assists.

[65] Clarkson ended the tournament with a win, beating Syria 109–55 with a 29-point performance earning the Philippines a fifth-place finish, its best in 16 years.

[66] In August 2022, SBP announced that they have accepted Clarkson as a naturalized player for the fourth window of the 2023 World Cup Asian qualifiers and future FIBA tournaments.