Heni was summoned by the police on December 28 and has been in custody since January 1st, after criticising the country's commerce minister in a radio show he hosts.
He was arrested under a law punishing the use of "telecommunications network to insult others," introduced by Tunisian President Kais Saied after he centralised power in 2021.
Tens of journalists and rights defenders gathered Wednesday morning in front of the court where Heni was tried, demanding his release and calling for freedom of the press in Tunisia.
"Today we're sad as we celebrate the 12th anniversary of the revolution after having gained freedom of speech only to find that we're losing it little by little through trials like this one," Fida Hammami, research and advocacy advisor at Amnesty International in Tunisia, said during the rally.
Seventeen journalists currently face trial in Tunisia, according to local media.
Many of them were prosecuted under the provisions of Decree-Law 54, which punishes "spreading false news" with up to 10 years in prison.
"Today, three of our colleagues are in prison under laws that have nothing to do with their journalistic work," Amira Mohamed, an executive member of the National Syndicate of Tunisian Journalists (SNJT), said before Heni's release.
"We are in danger when we no longer have access to information and we can no longer inform citizens."
Heni became well known during the 2011 uprising that ousted Tunisian dictator Zine El Abidine Ben Ali and set in motion what later came to be known as the Arab Spring.
He is still facing another charge on which he is yet to be tried, after comments he made in January 2023.
The 59-year-old journalist was "one of dozens of individuals who have been arbitrarily arrested and prosecuted by Tunisian authorities since President Kais Saied's power grab in July 2021 simply for exercising their right to freedom of expression," Amnesty International said Tuesday in a statement.
"Instead of prosecuting journalists for expressing their views, the authorities should uphold the hard-earned right to freedom of expression and end reprisals against criticism and dissent," it added.
A number of Tunisian opponents are currently behind bars, including Rached Ghannouchi, 82-year-old leader of Saied's political nemesis Ennahdha party, and Jawhar Ben Mbarek, co-founder of the National Salvation Front, the country's key opposition coalition.
In early 2023, Tunisian authorities carried out a string of arrests of more than 20 opposition figures, businessmen and former ministers, whom Saied deemed "terrorists" and jailed over an alleged "plot against state security."
TUNIS - A Tunis court released journalist Zied El Heni on Wednesday night with a six-month suspended sentence, his lawyer Jammel Hammami told AFP.