[3] The son of Warwick Gillard and Georgina Campbell, Campbell-Gillard commented that he never knew his father, saying "I don't speak to him.

[11] On 6 October 2013, Campbell-Gillard played in Penrith's Holden Cup Grand final against the New Zealand Warriors, starting at prop in the 42-30 victory.

[15] On 19 October 2014, Campbell-Gillard would again play for Fiji against Lebanon in the 2014 Hayne/Mannah Cup, starting at prop in the 40-28 win at Shark Park.

[21] In Round 23 against the New Zealand Warriors, Campbell-Gillard scored his first NRL career try in the 24-10 win at Penrith Stadium.

On 26 September 2015, Campbell-Gillard played for the Prime Minister's XIII against Papua New Guinea, starting at prop in the 40-12 win in Port Moresby.

[25] Campbell-Gillard had 2 vertebrae fractured and couldn't change out of his playing kit for 2 days due to the seriousness of the injury.

On 4 October 2017, Campbell-Gillard was awarded with the Merv Cartwright Medal as the Penrith Panthers Player of the Year.

[31][32][33] On 27 October 2017, Campbell-Gillard made his international debut for Australia against England, playing off the interchange bench in the 18-4 win at AAMI Park.

[36][37] Campbell-Gillard started the 2018 NRL season in good form up front as the Penrith Panthers were holding into a spot in the top 4.

[38][39] On 6 June 2018, Campbell-Gillard made his representative debut for New South Wales in Game 1 of the 2018 State of Origin series against Queensland, starting at prop as the Blues won 22-12 at the MCG.

[44] He made a total of 21 appearances for Parramatta in the 2020 NRL season as the club finished third but were eliminated from the finals in straight sets.

[48][49] In late October 2021, Campbell-Gillard announced he was not activating his player option, which would make him a free agent in 2023.

[50] On 19 June, Campbell-Gillard was not selected for game two of the series after New South Wales had lost the opening match 16-10.

[54] Campbell-Gillard played for Australia in the 2021 Rugby League World Cup final where they defeated Samoa 30-10 to claim their 12th title.

[56] On 26 April, the Parramatta club announced Campbell-Gillard would be ruled out for at least two months with a high grade groin injury.