While McInnes's future has been the subject of much consternation over the past month, NRL.com understands the Sharks have snuck under their traditional rivals' nose with a lengthy deal worth around $500,000 a season for the St George Illawarra skipper.
No comment has been made by Cronulla or the Dragons at this stage.
McInnes informed teammates of his departure on Tuesday morning after negotiations with the Sharks began before Christmas.
