He is considered one of the best halfbacks of all time, and is predicted by several previous greats of the NRL including Cameron Smith, Andrew Johns, Cooper Cronk, and Johnathan Thurston to become the greatest player in history, should his career continue on its current trajectory.

He appeared for the Windsor Wolves in the Ron Massey Cup and Sydney Shield in a handful of games,[12][13] before being called into Penrith's National Youth Competition (under 20) squad mid-season.

[20] Two days after the signing, in round 13, Cleary made his NRL debut for the Penrith Panthers against the Melbourne Storm at five-eighth.

[21][22][23] The next week against the Manly-Warringah Sea Eagles, Cleary scored his first NRL try, as well as kicking five goals in Penrith's 31-24 win at Brookvale Oval.

[24] Following a man of the match performance against the South Sydney Rabbitohs in round 15, The Daily Telegraph said of Cleary: "[it's] hard to believe he is only 18 playing his third NRL game.

[32] Cleary started the 2018 season as possibly the NRL's form player before suffering a knee injury in Round 3 against Canterbury-Bankstown where Penrith lost 20-18 at ANZ Stadium.

[35] On 6 June 2018, Cleary made his debut for New South Wales in Game 1 of the 2018 State of Origin series against Queensland, starting at halfback in the 22-12 win at the MCG.

In Round 4, Cleary kicked a goal from the sideline after the final siren to send their game against the Wests Tigers into extra time.

[45] In the 2020 qualifying final against the Sydney Roosters, Cleary scored a hat-trick and kicked a field goal in Penrith's 29–28 victory.

Cleary's below-par performances in the NRL grand final and the first State of Origin match are directly related to the pressure imposed on his kicking game.

[54] Cleary kicked eight goals for New South Wales in the opening game of the 2021 State of Origin series as they defeated Queensland 50-6.

[63] In game 2 of the 2022 State of Origin series, Cleary scored two tries and kicked eight goals in New South Wales 44-12 victory over Queensland.

[67] In the 2022 Qualifying Final, Cleary returned to the Penrith side and put in a man of the match performance in the club's 27-8 victory over Parramatta.

[72] On 18 February, Cleary played in Penrith's 13-12 upset loss to St Helens RFC in the 2023 World Club Challenge.

[73] In round 4 of the 2023 NRL season, Cleary kicked a two-point field goal from 40 metres out with seconds remaining to tie the game between Penrith and Parramatta at 16-16.

[76] In round 7, Cleary kicked two field goals including the winner during Penrith's 16-15 golden point extra-time victory over Newcastle.

Cleary won the Clive Churchill medal as man of the match after he inspired the Penrith side to come back from a 16 point deficit with less than 20 minutes to go, the largest successful Grand Final turnaround of NRL history despite suffering a grade 3 torn PCL in the ninth minute of the match.

With star team-mates Jarome Luai (shoulder), Isaah Yeo and Scott Sorensen (both HIA) forced from the field, Cleary remarkably orchestrated the comeback effort with involvements in all three tries.

[85][86] In round 20, Cleary made his return to the Penrith team and kicked a two-point field goal in golden point extra-time as they defeated the Dolphins 28–26.

In round 24, Cleary suffered a shoulder injury in Penrith's narrow loss to Melbourne and was ruled out for an indefinite period.

[89] Cleary played a total of 13 matches for Penrith in the 2024 NRL season including the clubs 14–6 grand final victory over the Melbourne Storm.

[90] Individual Penrith Panthers New South Wales Australia Cleary is co-owner of Drink West Brewery with Tyson Pedro and Tai Tuivasa.

Cleary was pictured at his home with a group of women on Anzac Day, and the photo was uploaded to social media.