The 23-year-old goalkeeper lasted just 15 minutes in their Group opener against England in Volgograd and was forced off after sustaining the injury in a collision with Manchester United midfielder Jesse Lingard.
Farouk Ben Mustapha replaced him and he is tipped to guard goal for the rest of the North Africans' campaign.
Besides Ben Mustapha, veteran Aymen Mathlouthi is another goalkeeping option for coach Nabil Maaloul.
Mouez will return to his French League 2 club Chateauroux for further treatment.
The former France youth international cannot be replaced as Fifa rules forbids teams to do so when the tournament is underway.
The France-born goalie had cemented his place as Tunisia’s first choice after switching international allegiance this year and debuted in a friendly match against Costa Rica in March.
Tunisia now face an enormous task to progress to the knockout phase after losing to England and they next meet a strong Belgium side.
Injury has dogged the Carthage Eagles' World Cup with star striker Youssef Msakni being left out of the tournament squad with a knee injury.
Star winger Wahbi Khazri and defender Ali Maaloul were injury worries in the run-up to the England game.
But Msakni is not looking at the injury concerns and feels their campaign in Russia is far from over.
“We still have six points to play for and we have to bring them home, God willing. I hope the mistakes we made will help us prepare for the next games,” Msakni told beIN Sports television.
Tunisia have never progressed past the group stages in four previous World Cup appearances.