Cahill had been due to fly home for the matches scheduled for Friday and next Tuesday in Canberra and Sydney.
However, club medical staff have insisted he needs more time to recover from the ankle injury he received after clashing with Manchester City defender Vincent Kompany in the Toffees' 2-0 defeat nine days ago.
Cahill was only just passed fit enough to play in the weekend's 216th Merseyside derby but now requires a period of rest.
"Tim played through the pain barrier on Saturday against Liverpool but the scan showed that the best course of action now is rest and rehab," the club's head of medicine Danny Donachie told evertonfc.com.
"Tim is disappointed but it is a straightforward decision because he would not be fit enough to play in the games in Australia."