Nicholls will join coach Wayne Bennett who he played under at the Rabbitohs. Bennett had promised not to poach any of his former players, but Souths are willing to let Nicholls out of his contract.
Nicholls captained the Rabbitohs during Round 25 as Bennett rested a host of players ahead of the finals campaign.
The news is a welcome boost for the expansion team who announced the acquisition of Storm forward Jesse Bromwich on another two-year deal late last week and now have six players on their roster.
Bromwich and Nicholls are joined by Melbourne and Queensland State of Origin second-rower Felise Kaufusi, Parramatta Eels heavy-hitter Ray Stone and Brisbane Broncos back Jamayne Isaako, as well as little-known rookie Valynce Te Whare.
News Corp are reporting Nicholls has signed a deal worth $500,000 for the two years.
Rabbioths CEO Blake Solly said Nicholls was a valuable member of the club, but the release made sense for him and his family.
“We appreciate Mark coming to us with this request early in the piece so we can plan for the future and we know he will give his all every time he plays for South Sydney throughout 2022, as he has since joining the Club for the 2018 season," Solly said.
“This new contract is a great opportunity for Mark, his wife Perrie and his family to set themselves up for life after football and we didn’t feel that it would be the right thing to do to stand in his way."
“Mark has, and will continue to, give great service to this Club and we look forward to supporting him and the team, alongside our Members, throughout the 2022 season.”
The Dolphins meanwhile, will now be able to possess a strong front-row combination of Nicholls and Bromwich.
Dolphins CEO Terry Reader said Nicholls was another excellent signing.
“Mark is a hard-working, no-nonsense type of forward that will fit straight into the Dolphins squad,” said Reader.
“He has had some real big-match experience with the Rabbitohs in the last few years, including playing in three straight preliminary finals as well as the most recent NRL Grand Final.
“We see him as someone who will not only add depth and experience to our squad, but a presence who will set an example for younger players on the value of hard work and persistence in the NRL.”