The landmark case has drawn international scrutiny of Hong Kong's judicial independence amid a years-long crackdown on rights and freedoms in the global financial hub after 2019 pro-democracy protests that Beijing saw as a challenge to its rule.
While 78-year-old Lai's supporters see him as a freedom fighter, Beijing sees him as a mastermind of the protests and a conspirator advocating for US sanctions against Hong Kong and the mainland. Chinese authorities have rejected accusations of eroding the city's rule of law.
"There is no doubt" that Lai "had harboured his resentment and hatred of" China for many of his adult years, Judge Esther Toh told a packed courtroom on Monday as the tycoon, wearing a pale green jumper and a grey jacket, sat with his arms folded.
The two other judges in his case were Alex Lee and Susana D'Almada Remedios.
Lai, the founder of the now-shuttered Apple Daily newspaper and one of the most prominent critics of China's Communist Party leadership, has already spent five years in jail, facing a slew of litigation under the sweeping security legislation Beijing enacted in response to the 2019 protests.
A pre-sentencing hearing where Lai can plead for lenience is scheduled for January 12. His lawyer Steven Kwan said Lai would decide whether to appeal after the sentencing.
Hong Kong leader John Lee and national security police chief Steve Li told reporters they welcomed the verdict.
"The judiciary is confident and unafraid of any intimidation and firmly discharges its responsibility to safeguard national security," the city's leader said at the airport before a regular visit to Beijing.
Lai, who suffers from health issues including diabetes and high blood pressure, was found guilty on two counts of conspiracy to collude with foreign forces and one of conspiracy to publish seditious material. He had pleaded not guilty on all counts.
The verdict bookends a year that marked the essential disappearance of Hong Kong's democratic opposition under pressure from Beijing. The Democratic Party voted to disband on Sunday.
Outside the court, people overnight formed a queue more than a block long, some with camping gear, seeking to attend the verdict.
Police were monitoring the area around the building.
Lai's trial began in December 2023 in the former British colony that reverted to Chinese rule in 1997, with the verdict seen as a potential fresh diplomatic flashpoint.
Countries including the US and Britain, as well as rights groups, say the trial is politically motivated and have called for Lai's immediate release.
US President Donald Trump raised Lai's case with Xi in a meeting in October and has said he would do his utmost to "save" Lai.
Beh Lih Yi, Asia-Pacific director of the Committee to Protect Journalists, called the verdict a "sham conviction" and "a disgraceful act of persecution."
"The ruling underscores Hong Kong's utter contempt for press freedom," she said. "Jimmy Lai's only crime is running a newspaper and defending democracy."
Other groups, such as Amnesty International, and pro-democracy activists who fled the city after the protests fearing prosecution have also condemned the verdict.
The Chinese and Hong Kong governments have said his trial was "fair and just" and the national security law treats all equally. They have said no freedoms are absolute when it comes to safeguarding national security.
