The 30-year-old man, who has Russian citizenship and is an asylum seeker, was also found guilty of possessing pornographic images of minors.
His pre-trial detention period of 11 months will be counted as part of his five year sentence, the judge said.
The trial began in January but the court had to adjourn twice - first because a witness from Germany did not turn up to his video conference hearing and a second time because the defence insisted on questioning further witnesses.
The trial took place amid tight security. The defence pleaded for a lighter conditional sentence, arguing that the man had no previous criminal convictions. However the judge ruled that there was “reasonable guilt” and said that the man had "ideological convictions".
Despite hours of interrogation it could not be proven that the man had actually undergone combat training in Syria and fought for Isis, nor that he had downloaded instructions on how to build a bomb from the internet.
He was sentenced for having "at least participated in armed exercises and for providing Isis members with food," the judge said. He also sent 800 US dollars to Syria and a message saying that he would return.
The Chechen had plead not guilty and said that he was only in Syria to help refugees who wanted to come to Austria get to the Turkish border.
He returned to Austria from Syria in 2013 - because he wanted to see an optician, according to the prosecution.
He was arrested last summer after police seized his mobile phone records. They found various selfies the man had taken in Syria and some pornographic images.
His lawyer told the ORF that he had “not expected such a sentence” and that he considered it to be overly harsh.
He can still appeal the sentence.