"Given the time that has elapsed since he was last seen on-board by other guests, with the deepest regret, and in consultation with the Joint Rescue Coordination Centre, we have accepted the expert view that there is unfortunately no likelihood of survival," the spokesperson said.
"The guest's family was notified and our care team is providing support at this difficult time.
"Guests on Golden Princess have been asked to keep the missing guest and his family and friends in their thoughts and prayers.
"The Melbourne-based Golden Princess is returning from a 13-night New Zealand cruise itinerary and scheduled to complete the cruise tomorrow."
news.com.au understands the man was not travelling alone.
The man could not be found after public announcements and extensive searches of the ship's cabins, common areas and technical spaces.
The Australian Maritime Safety Authority was told of the missing passenger about 9pm on Monday night.
"Victorian Police will prepare a report for the Coroner."
The Golden Princess left Adelaide on January 7 and took in Kangaroo Island and Melbourne before beginning its 13-night round trip to New Zealand, stopping at Fjordland National Park, Dunedin, Akaroa, Wellington, Gisborne, Tauranga, and Auckland.
It was scheduled to return to Melbourne yesterday before arriving back in Adelaide on Friday.
This is the second passenger to have gone missing from the Golden Princess in recent years.
A 61-year-old American tourist, who was travelling alone, was believed to have fallen from the ship after it left New Caledonia for Australia in 2017.
Princess Cruises said at the time the incident was being treated as a man overboard case.
WHERE TO GET HELP
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• LIFELINE: 0800 543 354 (available 24/7)
• SUICIDE CRISIS HELPLINE: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757