Tupou played his junior rugby league for the Berala Bears and Guildford Owls before being signed by the Parramatta Eels. Tupou played for the Eels' NYC team in 2010 and 2011, scoring 9 tries in 22 games, before being signed by the Sydney Roosters.
On 26 February, Tupou extended his contract with the Roosters to the end of the 2015 season. He became a full-time first grader in 2013, scoring 14 tries from 26 games. His most impressive try came in the 2013 NRL Grand Final when he leapt over Manly's David Williams to level the game at 6-6. Roosters went on to win the Grand Final 26-18 against the Manly-Warringah Sea Eagles. Tupou was named in the 24-man Tongan 2013 Rugby League World Cup squad. He made his Tongan international debut against Scotlandon the wing in the 26-24 loss at Derwent Park. Tupou played in all of Tonga's 3 matches in the tournament.
Tupou was again selected for New South Wales City. He played for New South Wales in Game 1 of the 2015 State of Origin series, in a 10-11 loss, but was dropped for the rest of the series. On 27 July, he re-signed with the Roosters, keeping him at the club to the end of the 2017 season. He finished the season having played in all of the Roosters' 27 matches and scoring 16 tries.
2016
In February, Tupou played for the Roosters in the Auckland Nines. He scored 10 tries from 21 games with the Roosters.
2017
In Round 4 against cross-city rivals the South Sydney Rabbitohs, Tupou played his 100th NRL match and scored a try in the Roosters 20-6 win at ANZ Stadium. In 2017 he elected to represent the nation of his ancestral heritage, Tonga. He played wing in every game of their stunning charge to the 2017 Rugby League World Cup semi-finals. He scored 2 tries in their win over Scotland in the pool stage of the tournament.
2018
Tupou was part of the Eastern Suburbs side which won their 4th minor premiership in 6 years. On 30 September, Tupou played on the wing in Easts 21-6 victory over Melbourne in the 2018 NRL Grand Final.
2019
In round 2 of the 2019 NRL season, Tupou scored 2 tries as the Sydney Roosters defeated Manly-Warringah 26-18 at Brookvale Oval. In round 21, Tupou scored 2 tries as his team defeated Canberra 22-18 at Canberra Stadium. Tupou made a total of 26 appearances for the Sydney Roosters in the 2019 NRL season as the club won their second consecutive premiership defeating Canberra 14-8 in the 2019 NRL Grand Final with Tupou playing on the wing. Tupou was involved in the match winning play late in the second half when he passed the ball on the inside to James Tedesco who raced away to score the deciding try. The premiership victory was Tupou's third as a player.
2020
On 22 February, Tupou played for the Sydney Roosters in their 2020 World Club Challenge victory defeating St Helens R.F.C. 20-12.