The club announced on Friday morning that the Sims would make the overseas move despite having a year to run on his contract.
He will join Hull Kington Rovers in 2021 on a three-year deal, which leaves the Dragons with three roster spots to fill for next season.
The Dragons also announced that front-rower Kaide Ellis has re-signed for one season.
The 24-year old joined the club halfway through the 2020 season and made eight first-grade appearances for the club.
Dragons General manager of football Ben Haran thanked Sims for his contributions to the club.
“I’d like to thank Korbin for his contribution at the Red V and wish him all the best in his future endeavours,” Haran told the club website.
“Kaide arrived at the Dragons in recent months with high credentials and he certainly proved a positive addition to our team in the back end of last season.
“The player market moves fast in rugby league and a lot of things can happen in a short amount of time.
“With three spots remaining on our roster, we’ll be working diligently over the coming months to ensure the players who do come to the Dragons are the right fit for our club.”
Sims arrived at at the club from Brisbane in 2019 and managed 21 NRL games over two seasons, getting hampered with injuries.