Flavien Moreau travelled to the conflict-ridden country at the end of 2012 but says he only managed to stay "a dozen days" as he was unable to stand a strict ban on smoking imposed by the Islamist militants he was with.
Moreau was sentenced on Thursday in Paris, after judges imposed the maximum sentence that had been sought by the prosecution.
In the same case, Farid Djebbar, 26, was sentenced to four years in prison, of which 18 months was suspended, for corresponding with Moreau and receiving money from him, although Djebbar did not leave the country.
Moreau, who is originally from South Korea and was adopted by a French family at a very young age, was not present in court to hear the sentence.
After a life of crime, for which he had 13 previous convictions, Moreau converted to Islam and had become radicalised prior to departing for Syria, where he joined a radical Islamist group.
He told the courtroom that he found a smuggler who took him to a Syrian village controlled by Islamist militants where he bought a Kalashnikov and munitions.
But he denied having done any fighting, saying he had only taken part in surveillance and policing.
"I found it really hard not to smoke... I had brought Nicorettes (an aid to stop smoking) but that wasn't enough. So I gave my weapon to my emir and left."
He returned to France to buy an electronic cigarette before attempting to go back to Syria, but he was picked up by French intelligence services.
It is estimated that around 150 French nationals have joined Isis forces since 2012, but estimates say hundreds more have left to fight jihad in Syria – all from varied backgrounds, dispelling widely-held beliefs that most are disadvantaged, lost youths, experts say.
In September it was reported that eleven members of the same family had left France for Syria for the same reason, while a couple from Orleans left with their three-year-old daughter to fight alongside Isis forces in the country.
by Lindsey Johnstone/AFP