The seven men were sentenced to six years in jail in October 2012 after a court in the medieval town of L'Aquila found them guilty of causing multiple deaths by having negligently downplayed the risk of the town being hit by a major earthquake just days before the killer tremor struck in April 2009.
But after a month-long appeal trial in the mountain town east of Rome, that verdict was overturned by a panel of three judges which concluded that six of the seven had committed no crime.
The judges partially upheld some of the charges against one defendant, Bernardo De Bernardinis but downgraded his sentence to a two-year suspended prison sentence that will not lead to him having a criminal record.
"The credibility of Italy's entire scientific community has been restored," said Stefano Gresta, the President of the National Institute of Geophysics and Volcanology, whose predecessor, Enzo Boschi, was one of the most eminent of the defendants.
Franco Coppi, one of the lawyers for the scientists, said: "It is very pleasing that our arguments have been upheld although we remain profoundly sorry for the families of the victims and understand their reactions."
But Stefania Pezzopane, an Italian senator and former president of the Aquila region, called the appeal decision "disconcerting and contradictory".
The precise reasons for the verdict will not be made clear until the full written judgement is released in several months' time. The prosecution may seek to have the convictions reinstated via a final appeal to a higher court.
The defendants had been backed by outraged scientists from across the world.
Numerous critics claimed that their prosecution had put science itself on trial, warning that experts would stop offering any kind of risk assessments if they were opening themselves up to potential litigation.
Perverse and ludicrous
Many compared the sentencing to the persecution of 17th-century astronomer Galileo, who, under threat of torture, was forced to recant his assertion that the Earth moves around the Sun.
The journal Nature called the original verdict "perverse" and the sentencing "ludicrous" given the acknowledged impossibility of predicting earthquakes.
The seven convicted men were all members of a Major Risks Committee which met in L'Aquila on March 31, 2009, six days before the 6.3-magnitude quake struck the town, triggering the collapse of many inadequately constructed buildings within its walls and in surrounding villages.
The 28-second quake, which struck in the middle of the night, left thousands homeless, and five years later L'Aquila has only partially been rebuilt.
The prosecution in the case had depicted the experts as having irresponsibly offered reassurances that persuaded citizens who might otherwise have sought refuge outside or in safer buildings to stay in their homes.
The Risks committee had been convened after a series of smaller tremors in the run-up to the deadly quake.
Key to the prosecution case was a statement by Bernardinis, then the deputy director of the Civil Protection Agency, describing the seismic activity as posing "no danger" to residents.
Although the defence pointed out that was only one of many observations made by the various committee members, the prosecution succeeded in persuading the solitary judge in the first trial that the experts had offered "disastrous reassurance" to L'Aquila citizens when they should have been making it clear there was a very real risk of a quake.
US writer David Wolman, who carried out a major investigation into the initial trial, concluded that the scientists had been unjustly convicted largely because of the difficulty many ordinary people have in understanding scientific advice.
"Where a career scientists hears the word 'improbable' and knows that rare events do occur, a non-scientist hears 'improbable' as shorthand for 'it ain't gonna happen,'" Wolman wrote in an essay on the case for online magazine Matter.