Crichton, once a schoolboy rugby star, is in the last season of his Roosters contract and is set to follow teammate Mark Nawaqanitawase out the door to the 15-man code.
Rugby Australia is expected to confirm Crichton's signing imminently.
The 29-year-old has been linked with moves to rugby union throughout his 198-game NRL career, notably when last coming out of contract in 2024.
Crichton ultimately signed a new two-year deal with the Tricolours but had remained open to a code switch in future.
He is set to play for Super Rugby Pacific franchise the NSW Waratahs and would be in the frame for Wallabies selection at the home World Cup next year.
Crichton will reunite with former Roosters teammate Joseph-Aukuso Suaalii at the Tahs following the young gun's highly-publicised move in 2024.
A graduate of famous rugby school Scots College, Crichton won the 2019 premiership in his first NRL season at the Roosters, having debuted with rivals South Sydney three seasons earlier.
At his peak, Crichton has been one of the NRL's most damaging second-rowers, enjoying a particularly strong 2024 that landed him back in the NSW State of Origin team.
Crichton won both the Brad Fittler Medal as the Blues' best player and the Dally M second-rower of the year award that season, his first full campaign after a mental health break delayed his start to 2023.
Daly Cherry-Evans, Siua Wong and Daniel Tupou are other high-profile Roosters players off contract after this season.
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