The two actors featured alongside Chris Pratt and Bryce Dallas Howard in the 2015 movie, which continued the franchise that started with Steven Spielberg''s 1993 film "Jurassic Park".
Johnson will returns as Lowery Cruthers, while Sy will come back as Barry, the assistant of Pratt''s Owen Grady, according to The Hollywood Reporter.
Colin Trevorrow is returning to direct the film that hails from Universal Pictures and Spielberg''s Amblin Entertainment.
The threequel will also feature the stars of the original film -- Laura Dern, Jeff Goldblum and Sam Neill.
Dern returns as Dr Ellie Sattler and Neill as Dr Alan Grant.
Goldblum, who made his comeback as Dr Ian Malcolm to the franchise with second chapter, "Jurassic World: Fallen Kingdom", is also set to reprise his role.
Emily Carmichael shares screenplay credits on "Jurassic World 3" with Trevorrow. Universal will release the movie on June 21, 2021. PTI RB RB