Bazley was selected with the 23rd overall pick in the 2019 NBA Draft. The 6-foot-8 forward made his league debut with the Thunder during the opening game of the season, Oct. 23 against the Jazz, recording three rebounds and one block in 19 minutes. The following game, the 19-year-old scored his first NBA bucket, posting five points, two rebounds and one steal against the Wizards in 15 minutes. The rookie had his first double-digit scoring performance Nov. 11 in an 11-point win over the Pelicans, recording 17 points, five rebounds and one block in 19 minutes. In a four-point win over the Grizzlies on Dec. 18, Bazley swatted a career-high four blocks in addition to four points and two boards in 11 minutes. The forward recorded a career-high two steals twice, Nov. 5 in a win over the Magic and Dec. 22 in a win over the Clippers. Bazley set a career-high 13 rebounds during a 13-point win over the Trail Blazers on Jan. 18, also recording nine points, one rebound and one block in 31 minutes. During the NBA bubble, on Aug. 9 in an 18-point victory over the Wizards, Bazley posted a career-high 23 points in addition to seven rebounds, one assist and one steal in 26 minutes. Just one day later, Aug. 10 against the Suns, Bazley secured the first double-double of his career, recording 22 points, 10 rebounds, three assists, one steal and one block in 35 minutes. Two days later, in a one-point win over the Heat, the rookie dished out a career-high four assists in addition to 21 points, nine rebounds, one steal and one block in 27 minutes. During seeding play, he averaged 13.0 points, 6.3 rebounds, 1.5 assists and 1.2 combined blocks-plus-steals in 27.5 minutes. The rookie appeared in all seven playoff games against the Rockets, averaging 6.6 points and 6.7 rebounds in 18.0 minutes.