McInnes, who can play in the hooking role, had previously been under contract to the South Sydney Rabbitohs and has played 39 NRL games to date.
The Botany Rams junior made his first-grade during the 2014 season against the Dragons at the Sydney Cricket Ground (Round 5) and captained the Junior Kangaroos later that year.
McInnes, 22, will commence training with the Dragons pre-season train-on squad in November.
St George Illawarra Dragons 2017 Player Movements
Levi Dodd (2017), Jacob Hind (2017), Josh Kerr (Melbourne Storm, 2019), Blake Lawrie (2019), Chris Lewis (2017), Nene Macdonald (Gold Coast Titans, 2021), Cameron McInnes (South Sydney Rabbitohs, 2021), Jordan Pereira (2020), Tristan Sailor (2019), Tariq Sims (Mid Season: Newcastle Knights, 2019), Paul Vaughan (Canberra Raiders, 2021)
Tom Carr (Canterbury-Bankstown Bulldogs), Mike Cooper (Warrington Wolves), Ben Creagh (retired), Dylan Farrell (retired), Sebastine Ikahihifo (Huddersfield Giants), Dunamis Lui (Canberra Raiders), Benji Marshall (Brisbane Broncos), Peter Mata'utia (Newcastle Knights), Adam Quinlan (Hull Kingston Rovers), Mitch Rein (Penrith Panthers)
Jai Field (2019), Tyson Frizell (2020), Reuben Garrick (2018), Patrick Herbert (2018), Luciano Leilua (2020), Jake Marketo (2017), Reece Robson (2019), Hame Sele (2018), Joel Thompson (2019)
|Off Contract 2018|