St George Illawarra have announced Shane Flanagan will join the Dragons' coaching staff in 2020 as an NRL assistant coach.

The Dragons exercised due diligence throughout the lengthy appointment process of Flanagan in consideration of his 2018 NRL coaching deregistration.

The former premiership-winning Sharks mentor will join the Red V on a one-year deal. The NRL have informed the Dragons that Flanagan can commence his role with the club in late-December.

"Shane will be a valuable asset to the Dragons' endeavours in 2020. His success has been proven time and time again over many years and we're glad to have him on board," coach Paul McGregor said.

The club are pleased to also confirm that Mathew Head will return as the Dragons' Canterbury Cup NSW coach in 2020.