Indiana Pacers / Mad Ants (2023–2024)
After going undrafted in the 2023 NBA draft, Tshiebwe joined the Indiana Pacers for the 2023 NBA Summer League. On 3 July 2023, he signed a two-way contract with the Pacers, splitting time with their NBA G League affiliate, the Indiana Mad Ants. On 9 December, he made his NBA debut in the 2023 NBA In-Season Tournament championship game against the Los Angeles Lakers, and recorded his first regular-season point on 13 December, against the Milwaukee Bucks.
On 18 February 2024, Tshiebwe was selected to the 2024 NBA G League Next Up Game, along with Mad Ants teammates Isaiah Wong and Kyle Mangas, where his team was crowned champions. Tshiebwe also participated in the 2024 NBA Rising Stars Challenge at All-Star Weekend, where his team lost in the finals to MVP and Pacers teammate Bennedict Mathurin. On 2 April 2024, Tshiebwe was awarded the NBA G League Rookie of the Year Award after leading the league in rebounding and set a new NBA G League single-season rebounding record with 16.2 rebounds per game. In 2023–24, he recorded 27 double-doubles, seven games with 20-plus points and 20-plus rebounds, broke the record for most rebounds collected in an Indiana Mad Ants season, and broke the Mad Ants record for most rebounds in a game with 28. He was also selected to the All-NBA G League 1st Team, as well as the All-NBA G League Rookie Team.