[2] Papali'i played his junior rugby league for the Te Atatu Roosters,[3] before being signed by the New Zealand Warriors.

[10] On 12 March, Papali'i was stood down by the Warriors due to a drink driving offence which had occurred on 1 January.

[11] "We expect better from our players and anyone who falls short of our standards will be appropriately dealt with irrespective of the time of year or their standing within the club," Warriors CEO Cameron George said, "Isaiah is extremely remorseful for his actions.

[14] He made his debut for Parramatta in round 1 of the 2021 NRL season, coming off the interchange bench in the club's 24-16 victory over Brisbane.

In September, Papali'i was awarded the Ken Thornett Medal as Parramatta's player of the season.

[21] Papali'i played a total of 28 games for Parramatta in 2022 including their Grand Final loss to Penrith.

[23] Papali'i played a total of 23 games for the Wests Tigers in the 2023 NRL season as the club finished with the Wooden Spoon for a second straight year.

Papali'i made 16 appearances for the Wests Tigers throughout the 2024 NRL season as the club finished with the Wooden Spoon for a third consecutive year.