Police Sgt. David Rose says the man and woman were discovered missing after the Carnival Spirit docked at Sydney’s Circular Quay Thursday morning.
He says a marine and air search is underway but gave no further details.
Australian Associated Press reports the search for the 30-year-old man and 26-year-old woman extends from Sydney 100 kilometers (60 miles) north to the city of Newcastle. Their nationalities have not been released.
A spokeswoman for ship operator Carnival Corp. was not immediately available for comment.
The Miami-based company is the world’s largest cruise operator and has been plagued by high-profile problems in recent years.