Dibaj became a Christian as a young man and joined the Jama'at-e Rabbani Church, the Iranian branch of the Assemblies of God. After the 1979 Iranian revolution he encountered difficulties. In 1983 he was arrested and imprisoned without trial in Sari and systematically tortured. He was finally tried by an Islamic court in Sari on December 3, 1993 and sentenced to death on charges of apostasy. At his trial Dibaj declared: "I am not only satisfied to be in prison for the honour of His Holy Name, but am ready to give my life for the sake of Jesus my Lord."
Following a worldwide outcry initiated by his friend and colleague Bishop Haik Hovsepian Mehr, Dibaj was finally freed in January 1994, although the death sentence was not lifted. Just three days later Haik Hovsepian Mehr was abducted and murdered.