Brown played for Parramatta's Harold Matthews and S. G. Ball squads. In 2017 he led the S.G. Ball Squad to the grand final where they were victorious 30-22 over the Cronulla-Sutherland Sharks. Later on in the year he went on to debut for the Eels in the U'20's Holden cup team in the middle of the 2017 season, at the age of 17. In 2017, Brown led the Holden cup squad to the NYC Grand Final, losing to the Manly-Warringah Sea Eagles. Brown was then selected in the Australian Schoolboys later in the year at five-eighth, but withdrew from injury. In 2018, Brown started the year with Jersey Flegg and training on and off with first grade. Towards the end of the year he debuted for the Wentworthville Magpies in the NSW Cup, playing 5 games. This led him to being promoted to Parramatta's first grade squad for the 2019 season, re-signing with the club until the end of the 2020 season. On 17 March 2019 Brown made his NRL debut in round 1 against the Penrith Panthers in a 20-12 win. On 24 March 2019 Brown scored his first NRL try in round 2 against the Canterbury-Bankstown Bulldogs in a 36-16 win. On 2 April 2019, Brown was ruled out indefinitely after sustaining bone bruising on his back. It was reported that Brown had been suffering with the injury for an extended period and would sit out opposed training sessions to protect himself in order to play in matches. In Round 15 against Canberra, Brown made his long awaited return from injury as Parramatta came from 16-0 down to win 22-16 at TIO Stadium in Darwin. At the end of the 2019 regular season, Parramatta finished 5th on the table and qualified for the finals. In the elimination final against Brisbane, Brown scored two tries as Parramatta won the match 58-0 at the new Western Sydney Stadium. The victory was the biggest finals win in history, eclipsing Newtown's 55-7 win over St George in 1944. The match was also Parramatta's biggest win over Brisbane and, at the time, Brisbane's worst ever loss since entering the competition in 1988. On 3 December 2019, Brown signed a three-year extension, until 2023, with Parramatta worth $2 million. In round 2 of the 2020 NRL season, Brown scored two tries as Parramatta defeated the hapless Gold Coast side 46-6.
