The Liberian-flagged Smyrni, carrying 135,000 tonnes of oil, was seized off the coast of Oman, the company said.
The company said it lost contact with the crew at 11:50 GMT on Thursday. The tanker is reported to be heading for Somalia.
Pirates based on the coast of northern Somalia prey on vital international shipping lanes in the area.
The hijacking is thought to have happened about 630 km from the Omani coast.
This was only the second voyage for the tanker, which first set to sea in 2011.