The European Causeway is currently five miles off the coast of Larne, according to tracking website Marine Traffic.
The website states the vessel’s automatic identification system status is set to “not under command” which is reserved for use when a vessel is “unable to manoeuvre as required by these rules and is therefore unable to keep out of the way of another vessel”.
The vessel left Cairnryan in Wigtownshire at about 12:00 BST and was due to arrive at Larne Harbour at 14:00.
P&O said the incident occurred due to a mechanical issue in the Irish Sea and a full inspection will take place when the ship is back in port.
It tweeted: “Due to a mechanical issue with the Causeway in the Irish Sea, tugs from Larne and Belfast were deployed to guide it back to port. Once the ship is back in Port a full inspection will take place
“Tugs from Larne and Belfast have been sent to guide it back to port.”
It is understood the Queen Victoria cruise ship, en route to Belfast for a refit, is also on site, along with a coastguard helicopter from Prestwick.
A RNLI spokesperson said that three lifeboats had been sent to the scene.