From ancient times up to now the following religions have been practiced in Iran: Paganism period, Mithraism (Mitra worshipping) period, Zoroastrian period and Islamic period. Besides the above several other faiths were followed by small minorities such as the followers of Mazdak and Mani and Christianity before the birth of Islam.
During the last 500 years, especially after the formation of the Safavid Dynasty, the Shia faith became the official faith of the Iranians. Presently 89% of the Iranian popular follow the Shia faith, 9th follow the Sunni faith, and the remaining 2% are Christians, Zoroastrians, Jews, and Bahais. Principle 12 of the Constitution of the Islamic Republic of Iran emphasizes that the Ja'fari version of Shia faith or 12-Imam faith is the official religion of Iran. According to the Constitution other Islamic faiths such as Hanafi, Shafeyee, Hanbali, Maleki and Zeidi Shia sect (4-Imam sect) is acceptable and respectable.
Also, Principle 13 of the Constitution says the Iranian Christians, Jews, and Zoroastrians are official minorities and are permitted to practice their faith and act according to the prescriptions of their faith.