The Lithuania international has been a regular starter for Brian McDermott's side in recent weeks and has made a total of 10 appearances since arriving at Elland Road in October.
McDermott told the club's official website: "We're delighted he's signed a new contract.
"When he first came in he signed short-term, but he's done very well and he's fitted in great with the group. It's great news."
Former Hearts skipper Zaliukas left Tynecastle in the summer and was snapped up by McDermott following a trial.
Leeds managing director David Haigh said: "Marius has done terrifically well since Brian brought him to the club and we felt it important to reward him and extend his contract with us.
"As we have already shown with new contracts for Ross McCormack and Alex Mowatt, we are constantly looking to the future, and Marius has a big part to play for us in that future.
"We're delighted he has signed, and we look forward to making further signings in January."