The court in Graz, the capital of Styria state, sentenced the imam to seven years in jail.
The three men received six-year, five-year and five-month suspended jail terms for their links to Isis in Syria.
Two other men were tried but acquitted.
All of the accused were born in Turkey and were found to be involved with the group founded by the 47-year-old imam, who has denied radicalizing young men to recruit them for Isis.
The others accused have also maintained their innocence, and the verdicts can be appealed.
Like other European countries, Austria saw a wave of people – many of them minors and some young women – leave the country to join Isis in Syria and Iraq.
In 2016, a Muslim preacher known as Ebu Tejma at the centre of an Austrian jihad propaganda network was sentenced to 20 years in jail for "brainwashing" dozens of people aged between 14 and 30.