Fitzgibbon made five appearances for Newcastle in the 2016 NRL season as the club finished last for a second consecutive year. He scored his first try in the top grade against North Queensland in round 13 of the competition.[11][12]
2017
Fitzgibbon made his first NRL appearance of the 2017 NRL season in round 10, going on to play in 14 matches and scoring 8 tries as the club finished last for a third straight season.[13] In September, he re-signed with Newcastle on a two-year contract until the end of 2019.[14][15]
2018
Fitzgibbon made 21 appearances and scored nine tries for Newcastle in the 2018 NRL season as the club finished 11th on the table.[16]
2019
Fitzgibbon played 21 games and scored five tries for Newcastle in the 2019 NRL season as the club finished a disappointing 11th on the table. At the start of the year, many tipped Newcastle to reach the finals after the club recruited heavily in the off-season.[17][18]
2020
He made 17 appearances for Newcastle in the 2020 NRL season including the club's first finals game since 2013 which was an elimination finals loss against South Sydney.[19]
2021
Fitzgibbon only 10 games for Newcastle in the 2021 NRL season and did not play in the club's elimination finals loss against Parramatta.[20]
2022
Fitzgibbon was limited to only nine appearances for Newcastle in the 2022 NRL season as the club finished 14th on the table.[21]
2023
Fitzgibbon made his 100th NRL appearance in March 2023 scoring a try for Newcastle in their 14–12 win over the Wests Tigers.[22] In July, Fitzgibbon signed a three-year contract with Super League side Warrington Wolves, starting in 2024.[23]
2024
On 8 June, Fitzgibbon played in Warrington's 2024 Challenge Cup final defeat against Wigan.[24]
Fitzgibbon played 14 matches for Warrington in the 2024 Super League season as the club reached the semi-final before losing to Hull Kingston Rovers.[25]