Adelaide 36ers (2020–2021) On 12 March 2020, Giddey signed with the
Adelaide 36ers of the
National Basketball League (NBL) as a part of the league's
Next Stars program to develop
NBA draft prospects, and he became the first Australian player to be a part of the program. Giddey turned down offers from several
NCAA Division I programs, including
Arizona. On 26 April 2021, he recorded 12 points, 10 rebounds and 10 assists in a 93–77 loss to the
New Zealand Breakers, becoming the youngest Australian in NBL history to record a
triple-double. In the 36ers' next game against the
Brisbane Bullets on 1 May, he became the first ever Australian to record a triple-double in consecutive games, finishing with 15 points, 13 assists and 11 rebounds in a 101–79 win. He had a third triple-double on 9 May in a 97–88 overtime win over the
Sydney Kings, finishing with 11 points, 12 assists and 10 rebounds. Giddey was released from the active playing roster on 17 May to prepare for the
2021 NBA draft, and finished the season averaging 10.9 points, 7.3 rebounds and a league-leading 7.6 assists per game in 28 games played. He was selected as the
NBL Rookie of the Year.
Oklahoma City Thunder (2021–2024) On 27 April 2021, Giddey declared for the
2021 NBA draft, where he was projected to be a
lottery pick. On 29 July, he was drafted as the sixth overall pick by the
Oklahoma City Thunder, and on 8 August, Giddey signed a contract with the Thunder. That same day, he suffered an ankle injury five minutes into his
NBA Summer League debut and was ruled out for the rest of the competition as a precautionary measure. On 20 October, Giddey made his NBA debut, putting up four points, 10 rebounds and three assists in a 107–86 loss to the
Utah Jazz. On 27 October, Giddey recorded his first double-double with 18 points and 10 assists in a 123–115 win over the
Los Angeles Lakers, while also becoming the third-youngest player to record at least 10 assists in a game, behind only
LeBron James, who did so twice. Giddey was named the NBA Western Conference Rookie of the Month for games played in October/November. On 26 December 2021, Giddey became the second player in NBA history, after
Norm Van Lier, to record a scoreless double-double, as he compiled ten assists and ten rebounds in the Thunder's 117–112 win over the
New Orleans Pelicans. Giddey was named the NBA Western Conference Rookie of the Month for games played in December. On 2 January 2022, Giddey became the youngest-ever player to record a triple-double, with 17 points, 14 assists and 13 rebounds in a 95–86 loss to the
Dallas Mavericks, surpassing the previous record set by
LaMelo Ball. Giddey was named the NBA Western Conference Rookie of the Month for games played in January and again in February, winning the award four consecutive times. On 27 March, Giddey was ruled out for the remainder of the season due to hip soreness, and finished the season averaging 12.5 points, 7.8 rebounds and 6.4 assists per game while shooting .419, .263 and .709 from the field, the three-point line and on free throws, respectively, with four triple-doubles. In addition, he was the sole rookie to tally at least 500 points, 400 rebounds and 300 assists. On 10 January 2023, in a game against the
Miami Heat, Giddey joined
Luka Dončić,
Ben Simmons and
Grant Hill as the only players in NBA history to record at least 1,000 points, 700 rebounds and 500 assists in their first 100 career games. On 15 January, Giddey scored a season-high 28 points along with nine rebounds and assists, leading Oklahoma City to a 112–102 win over the
Brooklyn Nets. On 12 April, during the
NBA play-in tournament, Giddey recorded 31 points, 10 assists and nine rebounds in a 123–118 win over the New Orleans Pelicans, advancing the Thunder to the eighth-seed game. On 11 January 2024, Giddey logged 13 points, 10 rebounds and 12 assists in 22 minutes against the
Portland Trail Blazers. In doing so, he became the first player in NBA history to post a triple-double on 100% field-goal accuracy in under 25 minutes.
Chicago Bulls (2024–present) On 21 June 2024, Giddey was traded to the
Chicago Bulls in exchange for guard
Alex Caruso. On 2 December 2024, Giddey put up a triple-double with 20 points, 13 rebounds and 11 assists in a 128–102 win over the
Brooklyn Nets. On 28 December, he put up a triple-double with 23 points, 15 rebounds and 10 assists in a 116–111 win over the
Milwaukee Bucks. He also became the first player in Bulls franchise history since
Jimmy Butler to record multiple games with triple-doubles in a season. On 8 March, he recorded his third triple-double of the season with 26 points, 12 assists, and 10 rebounds in a 114–109 victory against the
Miami Heat. On 22 March, Giddey recorded a near
quadruple-double (the last quadruple-double was achieved in 1994) with 15 points, 17 assists, 10 rebounds, and a career-high eight steals in a 146–115 win over the
Los Angeles Lakers. On 27 March, Giddey put up a triple-double with 25 points, 14 rebounds, 11 assists, and hit a buzzer-beating game-winner from half court in a 119–117 win over the Los Angeles Lakers. This was Giddey's 5th triple-double of the season and he joined
Michael Jordan as the only Bulls in franchise history to have 5+ triple-doubles in a single season. On 9 April, in a 119-111 win over the
Miami Heat, Giddey had 28 points, 16 rebounds and 11 assists while tallying his 7th triple-double of the season. Giddey also joined Michael Jordan and
Scottie Pippen as the only Bulls players to have seasons with at least 1,000 points, 500 rebounds, and 500 assists. On 9 September 2025, Giddey signed a 4-year, $100 million contract to return to the Chicago Bulls. On 31 October, Giddey scored a career-high 32 points along with 10 rebounds and nine assists in a 135–125 win over the New York Knicks, leading the Bulls to their first 5–0 start since the
1996–97 season.{{cite web|title=Josh Giddey scores 32 for undefeated Bulls in win vs. Knicks ==National team career==