Owner Fairdeal Group said the 12,800-dwt Fair Artemis (built 2008) made contact again on Wednesday night.
The cargo of gasoil has been stolen, but all 24 crew are safe.
The tanker had been missing for a week off Ghana.
The owner's fleet director John Gray said: "We have spoken to the captain of the vessel and are delighted to say that everyone on board is safe.
"The families and appropriate authorities have been contacted."
He added: “More details of events will undoubtedly become clear. So far we can say that the ship was boarded by a number of pirates, who have stolen the cargo and other items on the vessel."
