The Parthians worshiped the cult of Mithra, the same Mithraism that was embraced by much of the ancient world. The spread of Mithraism over the entire Roman Empire, the absorption into Christianity of Mithraic beliefs, rites and practices, ceremonies and festivals are a reflection of the influence of the Parthians on the ancient world.
It is also believed that Parthians widely practiced Zoroastrianism, and the holy documents of this religion were first compiled by the Parthians and used by the Sasanians. The ostraca found at Nisa confirm the connection with numerous place names that are Zoroastrian in character, but there as yet is no evidence of a flourishing Zoroastrian cult in Nisa. Also, the ostraca are dated in the Parthian with Zoroastrian month names. [Frye (1963), p. 175]
This page last updated 18 Jun 2019