The search involved a coastguard helicopter from Prestwick, a coastguard fixed-wing aircraft from Doncaster and air-scenting search and victim recovery dogs from Northern Ireland.
The rescue operation took place within the Irish Sea and Loch Ryan and lasted for over six hours.
However, it was eventually understood that the two people missing were initially down as foot passengers and left the ferry via a van.
No one was notified so the crew assumed the two people were missing – hence the rescue operation.
CCTV footage later showed the two men hitching a lift with the van.
Police on both sides confirmed that both passengers were safe and well.
Coastguard rescue teams from Stranraer, Portpatrick and Ballantrae along with Portpatrick and Stranraer RNLI lifeboats searched the Scottish side.
Portpatrick Coastguard were tasked to incident at 12.25am and Stranraer RNLI lifeboats went out at 1.07am.
Stranraer ILB carried out a search of North Loch Ryan covering the inner east and west sides of the loch.
At 4.05am, after completing the search, Stranraer ILB stood down, recovered and was made ready for service.
Northern Ireland’s K9 search and rescue team, as well as coastguard rescue teams from Portmuck, Bangor and Larne and a RNLI Larne lifeboat, were also launched.
The incident was logged by HM Coastguard as a ‘false alert with good intent’.
A Maritime and Coastguard Agency spokesperson said: “HM Coastguard assisted Police Service Northern Ireland and Police Scotland in response to a reported incident on the Larne to Cairnryan ferry route.
“Portpatrick, Larne and Stranraer RNLI lifeboats were sent as well as Port Muck, Kirkcudbright, Bangor and Ballantrae Coastguard Rescue Teams.
“The HM Coastguard Search and Rescue Helicopter from Prestwick and HM Coastguard fixed-wing aircraft from Doncaster also assisted.”