[5] In September 2019, O'Brien signed a three-year contract to become the Head Coach of the Newcastle Knights starting in 2020.
[3] Newcastle demonstrated a marked improvement in performance over previous seasons, finishing in 7th place and reaching the first of week of finals.
[8] O'Brien guided Newcastle to a 7th placed finish in the 2021 NRL season as the club qualified for the finals.
One security guard spoke to the media about the incident saying “The coach was arrogant and belligerent and even used the old, ‘Don’t you know who I am?’ line when we escorted him out of the men’s room and told him to cool it".
[11][12] This was later refuted by the Newcastle club in a statement which read "Reports alleging those Knights staff were intoxicated, disruptive and ejected from the venue are incorrect.