Brisbane Bullets Harrison joined the
Brisbane Bullets of the
National Basketball League (NBL) as a development player for the
2017–18 season. He averaged 6.2 points, 5.7 rebounds, and 1.2 blocks in 17 games. He was ruled out for six weeks in late November 2022 with a knee injury. On 6 March 2023, Harrison re-signed with the Bullets on a two-year deal. On 29 September 2024, Harrison signed a two-year contract extension with the Bullets. On 12 October 2024, he recorded 21 points and 17 rebounds (12 offensive) in an 87–85 win over the
South East Melbourne Phoenix. His 12 offensive rebounds set the record for the most ever by a player in a 40-minute NBL game. On 6 December, he recorded 19 points and 18 rebounds in a 102–83 win over the
Adelaide 36ers. He suffered a head knock in early January 2025 and missed the rest of the season with post-concussion symptoms. He was named the
NBL Most Improved Player for the 2024–25 season. On 19 September 2025, Harrison had 24 points and 15 rebounds in the Bullets' season-opening 104–95 win over the
New Zealand Breakers. On 15 October, he recorded 27 points and 15 rebounds in a 110–93 win over the
Perth Wildcats. He was sidelined between round 15 and round 21 due to a concussion.
QBL/NBL1 North, New Zealand NBL, and Puerto Rico In 2017, Harrison debuted in the
Queensland Basketball League (QBL) for the South West Metro Pirates. He continued with the Pirates in the 2018 QBL season. Harrison joined the
Nelson Giants of the
New Zealand NBL for the
2019 season, where he averaged 13.1 points, 6.2 rebounds, 1.2 steals and 1.2 blocks in 18 games. In 2020, Harrison played for the Southern Districts Spartans in the Queensland State League (QSL). Harrison joined the
Franklin Bulls for the
2023 New Zealand NBL season but injury restricted him to just seven games while averaging 14.7 points and 8.6 rebounds per game. Harrison began the
2024 New Zealand NBL season with the
Manawatu Jets before joining the Southern Districts Spartans of the
NBL1 North for the rest of the
2024 NBL1 season. With the Spartans, he averaged 23.6 points, 12.1 rebounds, and 2.4 blocks per game, earning selection to the NBL1 North First Team. In March 2025, Harrison joined
Indios de Mayagüez of the
Baloncesto Superior Nacional (BSN) for the
2025 season. In July 2025, Harrison joined the
Denver Nuggets for the
2025 NBA Summer League. Waardenburg re-joined Indios de Mayagüez for the 2026 BSN season. == National team career ==