By Agence France-Presse
The case comes as the ride-hailing app encounters regulatory roadblocks around the world -- it pulled out of Taiwan last month following an impasse with the government, which deems the service illegal.
It also on Wednesday promised not to use a recently uncovered "Greyball" software program to trick regulators trying to catch drivers breaking the law.
The Hong Kong drivers were arrested in a dramatic police swoop in 2015 after furious traditional cabbies in the southern Chinese city smashed up their own taxis with hammers and drove slowly towards the government headquarters calling authorities to act over unlicensed cars.
All five drivers were found guilty Friday at the West Kowloon Court of driving without a permit allowing them to transport paying customers and without third-party insurance, local media said.
They were fined HK$10,000 (US$1,287) each and had their driving licences suspended for 12 months, pending appeals.
"Sharing a ride shouldn't be a crime," Uber said in a statement in response to the verdict.
"We are very disappointed with today's court decision, which we believe goes against the best interests of riders, drivers and the city of Hong Kong itself," it said, adding that it would "stand by" and provide assistance to those involved.
"The transport law is from over 40 years ago," Uber Hong Kong general manager Kenneth She told reporters after the verdict.
"We hope that the government does not only look at outdated laws but truly takes a step forward" he said.
Ahead of the verdict, She told the South China Morning Post that Uber would not withdraw from Hong Kong.
The US firm announced in February it would suspend business in Taiwan after the government raised the maximum penalty for Uber drivers to Tw$25 million (US$804,000) -- the highest in the world.
Uber also halted services in Hungary in July last year due to new legislation that stops drivers from making money with their own vehicles.
It has also faced stiff resistance from traditional taxi drivers around the world, as well as bans in some places over safety concerns and questions over legal issues, including taxes.