Among them are three prominent activists, seen as figureheads of Hong Kong’s pro-democracy movement.
They could be jailed for up to seven years for their part in the “Umbrella Movement” protests of 2014.
Thousands marched demanding the right for Hong Kong to choose its own leader.
Those convicted include the so-called “Occupy trio” – sociology professor Chan Kin-man, 60, law professor Benny Tai, 54, and Baptist minister Chu Yiu-ming, 75.
They are seen as the founders of the movement that galvanised protesters in their campaign of civil disobedience.
“No matter what happens today… we will persist on and do not give up,” Mr Tai told reporters ahead of the verdict.
Mr Tai, Mr Chan and five others were found guilty of two charges of public nuisance, and Mr Chu and one other of just one charge.
The nine defendants walked into the court building looking refreshed and in high spirits. All but one said a few words in what might have been their last hours of freedom before their predicted jail term.
Delivering his verdict, Justice Johnny Chan said the defendants had caused a nuisance – by occupying major roads – leading to injuries among civilians. The nine looked calm and not particularly emotional. They were later released on bail. Benny Tai, Chan Kin-man and Chu Yiu-ming smiled as they passed me, as if it was just another day.
They are yet to say if they will appeal. The court was adjourned for the day as the lawyers are yet to finish their mitigation submissions. The sentences have yet to be announced.
The broader pro-democracy camp already has bad relations with Beijing. Activists and politicians did express their anger but political analysts also warn that people might simply leave the movement out of frustration.
“Some people might feel dispirited and helpless. I hope they can see that other people haven’t given up,” Benny Tai told BBC News Chinese ahead of today’s verdict.
Seventy nine days of sit-in protests have already changed Hong Kong a lot. But today’s verdict might serve more as a reminder that this city remains divided.
What has the reaction been?
At the trial Judge Johnny Chan rejected the idea that this would have a substantial impact on society.
“It cannot be reasonably argued that a charge of conspiracy to cause public nuisance would generate a chilling effect in society,” he wrote in his ruling.
But rights groups criticised the ruling, with Humans Rights Watch saying the court was “sending a terrible message”.
“[This] will likely embolden the government to prosecute more peaceful activists, further chilling free expression in Hong Kong,” said researcher Maya Wang in a statement to the BBC.
Lord Chris Patten, the last British governor of Hong Kong, released a statement saying that it was “appallingly divisive to use anachronistic common law charges in a vengeful pursuit of political events which took place in 2014”.
This verdict comes after a string of frustrations for pro-democracy activists. In the last few years the courts have removed six lawmakers for changing their swearing in oaths to include protest phrases. Others have also been disqualified from running for office.
The protests started in reaction to a decision made by China that it would allow direct elections in 2017, but only from a list of candidates pre-approved by Beijing.
Beijing is highly sensitive about Hong Kong’s status and any calls for more autonomy from China.
The former British colony was handed back in 1997 on condition it would retain “a high degree of autonomy, except in foreign and defence affairs” for 50 years.
Many people in Hong Kong believe they should have the right to elect their own leader.
In 2014, the three activists’ calls for non-violent civil disobedience joined with student-led protests and snowballed into the massive demonstrations.
Tens of thousands of people camped in the streets and demanded the right to fully free leadership elections.
The protests became known as the “Umbrella Movement” after people used umbrellas to shield themselves from pepper spray fired by police to disperse the crowd.
Protesters accused the Chinese government of breaking its promise to allow full democracy in Hong Kong, and of encroaching more and more on the region.
But the number of protesters dwindled to just a few hundred as the weeks dragged on and they ultimately failed to achieve their goal.