The ship was sailing from Cannes to Palma de Mallorca when the incident happened in the early hours of Saturday morning (8 June).
NCL said the guest, a 63-year-old Korean woman, had not been found.
"As soon as the report was made, the authorities were notified and a search and rescue operation ensued," the line said in a statement.
"The search has now ceased, and sadly, the guest has not been found. Our thoughts and prayers are with the individual’s family during this difficult time."
Due to the search, the ship’s planned call in Palma de Mallorca was cancelled.
It returned to Barcelona on Sunday (9 June) as scheduled.