Costas Vaxevanis, a 46-year-old veteran television journalist who now publishes a magazine, insists he was doing his job while ministers responsible for vetting the list for possible tax evasion did nothing for two years.
"We will endure this," Vaxevanis tweeted ahead of the trial.
Vaxevanis, who was arrested on Sunday, has been charged with breach of privacy and faces a maximum three-year prison sentence if convicted.
His lawyers, who reject the charges as "vague", have said that a number of people whose names Vaxevanis published will testify in court in his defence.
The head of the International Federation of Journalists, Jim Bumelha, said
he had testified on Vaxevanis' behalf and called the trial an "absurd farce".
"We were all astonished (by the arrest)," he told reporters.
Vaxevanis has accused the Greek state of hypocrisy and says the justice system is bowing to a corrupt political system.
"Our politicians declare themselves to be democrats. I see no evidence of this," he wrote in the Britain's The Times newspaper on Thursday.
"I wonder if Greek justice will show that the law safeguards the public interest and freedom of speech (. . .) in journalism you must do what you think is right without worrying about the consequences," he wrote.
Vaxevanis' "Hot Doc" magazine on Saturday published the names of more than
2,000 Greeks, allegedly from a controversial list of HSBC account holders.
The list was originally leaked by a Geneva bank employee to the French government and passed on to Greece in 2010 by France's then finance minister Christine Lagarde.
Viewing the list as stolen data that could not be used against potential tax evaders, the Greek authorities took no action for two years.
When the case resurfaced last month, it took several days for officials to even locate a copy of the so-called "Lagarde List".
Among those named are prominent businessmen, shipowners, lawyers, doctors,
journalists and a former minister, as well as companies, housewives and students although no deposit sums were published.
The data has been the subject of intense discussion, with the government facing calls to use it to crack down on potential tax cheats as the country grapples with a massive debt crisis.
On Thursday, a special economic prosecutor asked parliament to investigate whether previous finance ministers could be faulted for failing to take action on the list, news reports said.
Officially, the prosecutor asked lawmakers to "investigate politicians of the period in question," a justice source said.
Evangelos Venizelos, the leader of the socialist Pasok party who was formerly finance minister, is among officials who could be called to testify.
Venizelos has already told a parliament committee that he had ordered the finance ministry's tax police to investigate, a claim which the department's chief at the time denies.
The first recipient of the data in 2010, ex-finance minister George Papaconstantinou, said he did not know what had happened to the original version of the list, raising speculation that it could have been tampered with.
As a result, current Finance Minister Yannis Stournaras has asked France to re-send the list.
Vaxevanis says he received the information in an anonymous letter whose sender claimed to have received it from a politician.
UPDATE: The Greek court late Thursday acquitted Vaxevanis of breaching privacy after a 12-hour hearing.
Judge Malia Volika declared the journalist's innocence and rejected all objections from the prosecution.
The ruling was met with applause, while Vaxevanis told Volika: "I thank you very much Madam Judge."
While leaving the courtroom, the journalist said: "I did what all journalists would have done."
During the trial, Vaxevanis stressed that he was obliged to publish the list.
"It is my job to publish this list, even if my father were on the list, I would have published it," he said.
Several media workers also testified on behalf of Vaxevanis, including the head of the International Federation of Journalists, Jim Bumelha, who called the trial an "absurd farce".