Sexton appeared in and started all 65 games for the Cavaliers during the coronavirus-shortened 2019-20 regular season. He set per-game career highs in points (20.8), rebounds (3.1) and steals (1.0) while also averaging 3.0 assists. Sexton also improved via career marks in field-goal percentage (47.2) and free-throw percentage (84.6) while hitting 38.0 percent of his threes. The young guard drained 1.5 three-pointers per game. In the NBA ranks at the March 12th sports stoppage, Sexton was 13th in total minutes (2,143), fourth in two-point field goal attempts (831) and 18th in points (1,349). Sexton arguably had his best all-around performance of the season Mar. 2 during a game against the Jazz. In 39 minutes, he accumulated 32 points (11-17 FG, 4-6 3Pt, 6-8 FT), five rebounds, three assists and three steals. It was one of his five games with at least 30 points, one of his eight games with at least four made threes, one of his 13 games with at least five rebounds and one of his 35 contests with at least three assists. Two nights later, the second-year guard scored a career-high 41 points, plus added six dimes, three boards and one steal, during a home loss to the Celtics. In his last eight games before the March 12th stoppage, Sexton averaged 28.1 points, 4.0 assists, 1.4 steals and 2.3 made threes per contest.

Sexton made his NBA debut in 2018 and quickly established himself as the starting point guard for the Cleveland Cavaliers. By the end of the 2018-2019 season, he started 72 of the Cavs' 82 games. And Sexton proved durable, having played in all of Cleveland's 82 matches. On Nov. 24, he registered a career-high 29 points against the Houston Rockets, leading his squad to a 117-108 upset. A few weeks later, on Dec. 8, the rookie duplicated that feat with another 29-point performance to power the Cavs to a 116-101 victory over the Wizards. For the season, Sexton averaged 16.7 points per game and scored 1,371 total points. Late in the season, he went on a scoring run and became the first rookie since Tim Duncan to break the 23-point barrier in seven-straight games. On Mar. 8, he sank his 76th three pointer of the year, breaking Kyrie Irving's Cavs rookie record for made treys. Sexton went on to finish the season with 119 made threes. In addition to scoring, he led his team with 243 assists and 2,605 minutes played. Sexton's Cavaliers ended the season at 19-63 and did not qualify for the playoffs. Sexton was later named to the 2018-19 All-Rookie Second Team.