[8] On November 10, 2016, Sexton committed to the Alabama Crimson Tide, on the same day he signed his letter of intent (LOI).

Following Alabama's loss in the 2018 NCAA men's basketball tournament, Sexton announced his intention to forgo his final three seasons of collegiate eligibility and declare for the 2018 NBA draft, where he was expected to be a first round selection.

[12] Before Alabama's exhibition game on November 6, 2017, the school announced that Sexton would not play due to eligibility concerns.

[17] On October 17, 2018, Sexton made his NBA debut, coming off the bench for the Cleveland Cavaliers with nine points and three rebounds in a 104–116 loss to the Toronto Raptors.

[19] On March 8, 2019, Sexton passed Kyrie Irving for 3 pointers made as a Cavs rookie with 76 against the Miami Heat.

Additionally, he is the only rookie in NBA history to have played at least 2,000 minutes while scoring over 16 points per game on over 40% 3-point accuracy and fewer than 3 turnovers.

He was named to the Rising Stars Game at the 2020 NBA All-Star Weekend as a replacement for injured Miami Heat rookie Tyler Herro,[20] where he put up 21 points, 5 rebounds and 3 assists[21] for Team USA.

On March 4, 2020, Sexton scored a season-high 41 points, alongside three rebounds and six assists, in a 106–112 loss to the Boston Celtics.

[25] On January 20, 2021, Sexton set a new career high of 42 points in a 147–135 double overtime win against the Brooklyn Nets.

[30] On November 7, Sexton exited a road game against the New York Knicks with a knee injury, which was later revealed to be a torn left meniscus.

[34][35] Sexton made his debut for the Jazz on October 19, recording 20 points, 5 rebounds, and 2 assists while coming off the bench in a 123–102 win over the Denver Nuggets.