In 2006, Webster joined the Hull Kingston Rovers as an assistant and academy coach. In 2008, he returned to Australia, spending a season with the Parramatta Eels on work experience. He returned to Hull KR in 2009 as an assistant coach, spending three more years with the club.
In 2012, he once again returned to Australia, this time as head coach of the Balmain TigersSG Ball Cup team and assistant to the Wests TigersNYC team. That year, Balmain won the SG Ball Cup for the first time in 30 years and would go onto win the Under-18 National Final over the Townsville Stingers.[6][7][8]
In 2013, Webster took over as head coach of the Parramatta EelsNYC team, winning just seven games. In 2014, he returned to the Wests Tigers as head coach of their NYC team, winning 16 games and reaching the finals.
After two seasons at the Warriors, Webster once again returned to the Wests Tigers in 2017 as an assistant coach.[10]
On 22 March 2017, Webster was named interim head coach of the Tigers after former head coach Jason Taylor was sacked three games into the season.[11]Ivan Cleary was announced as the new head coach on 3 April 2017.[12]
Webster would go on to win back-to-back Premierships with the Panthers in 2021 and 2022. During round 9 of the 2022 NRL season, Webster coached Penrith for one NRL game when head coach Ivan Cleary was absent, along with fellow assistant coach Cameron Ciraldo.[13][14]
New Zealand Warriors
On 8 July 2022, the New Zealand Warriors announced that Webster had been appointed as their head coach, beginning with the 2023 season.[15][16] Webster led to the Warriors to a top four finish, and the club's first home semifinal since 2007, during a highly successful first season in charge.[17]
On 27 September 2023, Webster received the Dally M Coach of the Year award, after taking the New Zealand Warriors to a preliminary final from 15th on the ladder in 2022.[18]
However, the club could not back up a strong 2023 season with the club finishing 13th on the table at the conclusion of the 2024 NRL season.[19]