Mojtaba Seyed Allaoding Hossein, Mohammad Reza Partoi (Kuroush), Vahid Hakani and Homayoun Shokuhi were arrested on February 7 this year after the security forces had raided their house meeting in Shiraz.
They were convicted of participating in house meetings, advertising Christianity, having connections with Christian Organizations abroad, propaganda against the government and disrupting the national security.
The Revolutionary Court in the city of Shiraz sentenced all of them to three years and eight months in prison.
Mr Hossein and Mr Shokuhi were also handed eight months suspended sentences and Fariba Nazemian and her 17 year-old son Nima Shokuhi were handed two year suspended prison sentences.