In 2016, Haas played for the Australian Schoolboys. In September 2016, he signed a 3-year contract with the Brisbane Broncos until the end of 2019, after weighing up offers from 10 NRL clubs, plus scholarship offers from American football college teams. In 2017, he played for the Broncos' NYC team. After impressing for the Broncos NYC side throughout the year, he was called in to act as an Andrew Fifita "clone" at a Queensland State of Origin opposed training session before game three of the 2017 series. In September 2017, he was named at prop in the NYC Team of the Year.
2018
In 2018, Haas played for the Broncos' Queensland Cup feeder side, Wynnum Manly Seagulls. In round 8 of the 2018 NRL season, he made his NRL debut for the Broncos against the South Sydney Rabbitohs. Commentator Phil Gould remarked that his debut game was "the birth of a superstar." He would go on to play two more games before missing the remainder of the season with an injured shoulder. In July 2018, the Broncos re-signed Haas on a 6-year contract.
2019
On February 19, Haas was suspended for 4 matches and fined $20,000 by the Broncos after the player failed to cooperate fully with the NRL integrity unit regarding an investigation into off-field incidents involving family members. Haas, while fasting for his first ever Ramadan after converting to Islam in early 2019, scored the first try of his NRL career against the Sydney Roosters in round 10 on Friday 17 May 2019 at Suncorp Stadium in Brisbane. On 26 May, Haas was selected in the New South Wales Blues Origin squad for Game 1 of the 2019 State of Origin series. This makes him the second most inexperienced player to play Origin having played only 10 NRL matches. Haas fasted for Ramadan up until the day before Game 1 of the 2019 State of Origin series on Wednesday 5 June 2019. Haas missed out on selection for Game 2 and Game 3 of the 2019 State of Origin series which New South Wales won 2-1. Haas made 21 appearances for Brisbane in the 2019 NRL season as the club finished 8th on the table and qualified for the finals. Haas played in the club's elimination final against Parramatta which Brisbane lost 58-0 at the new Western Sydney Stadium. The defeat was the worst in Brisbane's history and also the biggest finals defeat in history. On 30 September, Haas was named at prop in the Australia PM XIII side. On 7 October, Haas was named in the Australian side for the upcoming Oceania Cup fixtures.
