[5][6] Despite playing for both Australia in junior representative teams, Trbojevic gained an ATAR of 94.3 in his HSC at Pittwater High School, achieving the top band for 2 and 3-unit mathematics.
[13] Trbojevic started 2015 playing fullback for Manly's NYC team and crossed for 4 tries in the opening game of the season against the Parramatta Eels at Pirtek Stadium.
He continued to play a starring role in the Under 20's as Manly won its first four games of the season until injuries forced first grade coach Geoff Toovey to promote him to make his NRL debut on the wing for Manly-Warringah in their round 5 game against the Canberra Raiders at the Lavington Sports Ground in Albury in country NSW.
[16] Due to the quality of the Manly backline which included representative players Brett Stewart, Jamie Lyon, Steve Matai, Peta Hiku and Jorge Taufua, Trbojevic has been forced to bide his time playing in the NYC while being used as an injury replacement winger for the Manly's NRL side.
[18] Despite only having played only 8 games in first grade in 2015, all of them on the wing, Trbojevic's talent as a fullback was recognised when he was named in the position for Rugby League Week's 2015 NRL Rookie Team of the Year.
[22] Trbojevic would play 23 games for the club in 2016, missing only round 9 due to a high ankle sprain suffered in the Anzac Day match against the Newcastle Knights.
Although hampered by the injury which would require corrective surgery at the end of the season, he continued playing and was rewarded mid-season when he and brother Jake were called into the New South Wales squad before Game 3 of the 2016 State of Origin series as development players.
His form was such that he was predicted to be selected on the wing for New South Wales until suffering an injury in a game against the Brisbane Broncos on 13 May.
With Brisbane winger David Mead flying through in his chase of the kick, Trbojevic was forced to leap to catch the ball and was tackled while in mid-air, coming down with his left leg buckling awkwardly underneath him.
[citation needed] At the end of the year, he was rewarded for this form with an Australian jersey, playing 2 games in the World Cup and scoring 1 try.
[citation needed] In round 4, Trbojevic injured his ankle in the final 10 minutes of the match and missed the following week's game.
[27][28] Trbojevic was retained for Game 3 of the 2019 State of Origin series which was won by New South Wales 26-20 at ANZ Stadium.
[30] Trbojevic started the 2020 NRL season off very well, recording solid performances against both the Melbourne Storm and Sydney Roosters.
[citation needed] Trbojevic made his injury return in round 19 of the 2020 NRL season against the Gold Coast Titans, where the Manly-Warringah Sea Eagles lost 24-42.
[33] In round 9 of the 2021 NRL season, he played his 100th first grade game and put in a man of the match performance as Manly-Warringah defeated New Zealand Warriors 38-32.
[35] On 30 May, he was selected for game one of the 2021 State of Origin series in which he was man of the match scoring a hat-trick in New South Wales’ 50-6 victory over Queensland.
[41] In round 22, he was involved in an accidental head knock with teammate Jason Saab, and was subsequently rested the following week as a precaution.
In the Final of the Pacific Championships against Tonga at home in Sydney, Trbojevic scored two tries and had two more disallowed by the bunker in the three minutes before halftime as Australia wrapped up the series with a 20–14 win.