The man went overboard on the Quantum of the Seas at about 11pm local time (early Wednesday night AEST), about 1400km south of the Hawaiian islands.
The US Coast Guard has now issued an Urgent Marine Information Broadcast – a widespread radio message to alert ships in the area to a distress situation – to all vessels in the Pacific Ocean, south of Hawaii, to help look for the man.
Coast Guards have been searching the site with a C-130 Hercules for the missing man to no avail so far.
After six hours of searching, the aircraft has been forced to run back to Hawaii to refuel.
The authority confirmed to 9News that the aircraft will continue searching for the missing man at first light.
The Coast Guard has also put out a call to the US Navy for aid.
Passengers were woken by the PA system calling “oscar, oscar, oscar” – the ship’s code for man overboard.
They were then asked to go back to their rooms and make sure all their travelling party was accounted for, while bright lights swept the water to search for the reported missing passengers.
About 90 minutes later, the passengers were told they could leave their rooms.
Passenger Georgina Thompson said she and her husband were in bed when they heard the alert call.
“There were lights, you know, the big lights shining on the ocean,” she told Today.
“And also there were a couple of boats out there in the water.”
The cruise ship, operated by Royal Caribbean Cruises, has been at sea for 15 days and was due to dock in Honolulu, Hawaii, soon, after a recent visit to Tahiti.
It departed Brisbane on April 12.
The man’s identity is not yet known, nor how he went overboard.
The Quantum of the Seas has resumed its course for Kona on Hawaii’s Big Island.
“While on its trans-pacific sailing, a guest onboard Quantum of the Seas went overboard,” Royal Caribbean said in a statement to 9News.com.au.
“The ship’s crew immediately launched a search and rescue operation and is working closely with local authorities.
“Quantum of the Seas departed Brisbane on April 12 and is scheduled to arrive in Honolulu (on) April 28.”