A cruise liner that went ahead with a voyage that led to a major COVID-19 outbreak misled passengers about safety and was negligent in its duty of care.

In a landmark judgment representing the first successful cruise ship class action in the world, the Federal Court found the operator guaranteed passengers would have a safe, relaxing and pleasurable cruise holiday on the Ruby Princess.

Instead, 663 positive cases were reported among the 2641 passengers, including 1679 Australians on board the ill-fated March 2020 voyage.

Twenty-eight people died during the outbreak.

One of the passengers, Susan Karpik, was the lead plaintiff in a class action against Australian charter company Carnival.

Carnival trades under the Princess Cruises name and is the operator of the Ruby Princess, a Bermuda-registered vessel.

Ms Karpik sought damages for personal injuries, distress and disappointment to the value of more than $360,000.

Her individual claim revolved around the stress and disappointment caused by the illness of her husband Henry, who had to be placed in an induced four-week coma after contracting the virus, and his ongoing care.

The Ruby Princess departed from Sydney for New Zealand on a 13-day round trip, but returned 11 days later when Australia's borders were shut in the early days of the pandemic.

Justice Angus Stewart found the cruise company knew or ought to have known about the heightened risk of COVID-19 infection on the vessel.

He said the company owed Ms Karpik a duty to take reasonable care for her health and safety, including the risk of harm from the virus.

"To proceed with the cruise carried a significant risk of a coronavirus outbreak, with possible disastrous consequences, yet they proceeded regardless," he said on Wednesday.

"The respondents were therefore negligent and in breach of their duty of care."

Justice Stewart also found Carnival had misled passengers with claims it was "reasonably safe" to embark on the cruise despite the heightened risk of contracting COVID-19 on board.

While Ms Karpik was successful on a claim for out-of-pocket medical expenses totalling $4423 plus interest, Justice Stewart found she did not suffer from long COVID.

As a result, she did not meet the non-economic loss threshold required to recover personal damages.

Justice Stewart found Ms Karpik was entitled to disappointment damages to compensate for the fact that the cruise was not a "happy and relaxing holiday" as advertised.

However, as Carnival refunded all passengers the cost of the cruise, the judge found the company had satisfied that claim.

Ms Karpik said she was pleased with the court's finding and hoped it would bring some comfort for other passengers.

"For me and other passengers, we've been through the mill and back. It's been a long journey," she told reporters.

"I do hope (the company) will take the time to read the information we've given them about our experiences and take better care of their customers."

The former nurse said she was not disappointed by the court's decision on damages.

Shine Lawyers joint head of class actions Vicky Antzoulatos said the findings were "a long time coming" and a comprehensive victory for passengers.

"This is the first successful cruise ship class action in the world, so other companies will be paying attention to this case," she said.

Other passengers would still need to prove their individual damages, unless Carnival settled all of the claims.

Ms Antzoulatos urged the company to resolve all compensation claims without further court action, given the outcome of the case.

Carnival Australia said it was considering the judgment in detail.

"The pandemic was a difficult time in Australia's history and we understand how heartbreaking it was for those affected," a spokesperson said.