In April 2022, Griffiths was announced as the head coach of the Newcastle Knights' NRLW team.[3] The team won 4 of its 5 regular season games, before winning the semi-final match and ultimately winning the 2022 NRLW Premiership, the Knights' defeating the Parramatta Eels 32–12.[9]
2023
Griffiths would coach the NRLW team to another premiership win in 2023,[10] before being announced as the Knights' NSW Cup head coach going into 2024.[11]
2024
On 1 July, the New Zealand Warriors announced the appointment of Griffiths as head coach of their NRLW team, who return to the competition in 2025. Griffiths was appointed on a three-year deal.[12] The Newcastle Knights confirmed that Griffiths will depart the club at the conclusion of the 2024 NSW Cup season.[13]