The Malaysian Maritime Enforcement Agency (MMEA) said in a statement that the ship, Vier Harmoni, has been located in the waters off Batam, Indonesia.
The MT Vier Harmoni was reportedly sailing from Tanjung Pelepas port in Malaysia on Monday when it was seized.
The identity of the hijackers is yet to be confirmed, MMEA added.
The diesel tanker was carrying an estimated value of 1.57 million ringgit ($392,795).