Marshall-King was born in Whakatāne, New Zealand. He is of Māori descent. He moved to Sydney, Australia at a young age played junior rugby league for All Saints Toongabbie, before being signed by the Wests Tigers.
In round 26 of the 2017 NRL season, Marshall-King made his NRL debut for the Tigers against the New Zealand Warriors.[5][6] He spent the majority of 2017 playing for the Tigers in the Intrust Super Premiership NSW competition, making 19 appearances in a side that finished last on the table.[7][8] In November, he signed a two-year contract with the Canterbury-Bankstown Bulldogs starting in 2018.[9]
Canterbury-Bankstown Bulldogs 2018-2022
In round 1 of the 2018 season, Marshall-King made his club debut for the Canterbury-Bankstown Bulldogs against the Melbourne Storm, coming off the bench at hooker in the Bulldogs' 18–36 loss at Perth Stadium.[10] In round 3, he earned the starting spot at five-eighth.[11]
Marshall-King played 23 games for Canterbury in the 2019 NRL season as the club finished 12th on the table.[12][13] He made twenty appearances for Canterbury in the 2020 NRL season. The club finished in 15th place on the table, only avoiding the wooden spoon by for and against.[14] Marshall-King made a total of nine appearances for Canterbury in the 2021 NRL season as the club finished last and claimed their sixth wooden spoon.[15]
Dolphins 2023-present
Marshall-King signed a two-year deal with the newly admitted Dolphins.[16] In round 1 of the 2023 NRL season, he made his club debut for the Dolphins as hooker in their inaugural game in the national competition, when they pulled off a major upset defeating the Sydney Roosters 28–18 at Suncorp Stadium.[17]
In total, Marshall-King played fifteen games and scored two tries for the Dolphins in 2023. He played a total of 17 games for the Dolphins in the 2024 NRL season as the club finished 10th on the table.[18]