The European Causeway had departed Cairnryan in Scotland at midday on Tuesday and was due to arrive at Larne Harbour in Northern Ireland two hours later.
But the vessel was left adrift five miles off the coast of Larne after a “mechanical failure” P&O had said.P&O said a full inspection will take place when the ship is back in port.
Three lifeboats from Larne and Red Bay were launched to check on the vessel.
One Twitter user claiming to be on the ferry complained of being left stationary without power for over an hour-and-a-half.
A P&O Twitter account replied: “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.”
They later added the fault had been resolved with tugboats sent out to rescue the ferry remaining “on standby”.
P&O said: “Following a temporary mechanical issue, the Causeway is now continuing to the Port under its own propulsion, with local tugs on standby.
“There are no reported injuries on aboard and all relevant authorities have been informed. Full and independent inspections will follow.”