The three migrants were jailed for five to six months for supplying false information to Austrian authorities after lying about their age.
The three men cheated the state out of more than €100,000, benefitting from health insurance, support, basic care, pocket money and German language courses.
The case against the three was brought after a court ordered medical reports which revealed that the men were older than stated on documents supplied during their asylum application.
Two of the accused denied the accusation of having unlawfully obtained the social benefits, claiming their parents were to blame as they wrote down the dates of birth according to the Afghan calendar (the Solar Hijri calendar).
This calendar, used only in Iran and Afghanistan, has six months of 31 days, then five months with 30 days each and finally one with 29 days, except in leap years where it has 30.
The pair said they did not know their own birth dates.
A lawyer for one of the two men said his mother was illiterate and could have easily made a mistake when giving his date of birth.
The third man admitted in court that he had lied about his age.
He said: "People said it was better to apply as a minor as then I cannot be deported back. I was afraid that I would then be killed in Afghanistan like my father was."
The judge did not believe that the first and second defendant were unaware of their real ages.
She said: "They knowingly gave false information so they could stay in Austria."
The three young men have been sentenced to five and six months in prison.
In the first 10 months of 2016, 16,054 minors, of which 4,076 were unaccompanied, applied for asylum in Austria.
Violent drug-dealing migrant arrested after hurling abuse at barman who denied him free food and drink
Norwegian Economy at the Mercy of Saudi Prince
Heroic German dad rescues terrified daughter from Syrian rapist then hauls him to police