The Parthian Empire inherited Persia and Mesopotamia from the Seleucids in 247 BCE, and with them inherited a Zoroastrian tradition that had already survived Alexander's conquest and two centuries of Hellenistic rule without disappearing. A history of Zoroastrianism treats the Parthian period as one of quiet continuity rather than dramatic change: the fire temples and priestly lineages that had served the Achaemenid court persisted under Parthian rule, even as the new dynasty itself, of nomadic Central Asian origin, governed a religiously plural empire that also included Greek cities, Babylonian temple cults, and, in its western territories, Jewish and early Christian communities.
Textual sources for the study of Zoroastrianism from this period are comparatively thin, since much of the Avesta's core material appears to have been transmitted orally through the Parthian centuries before being committed to writing under the Parthians' Sasanian successors, who claimed a more overtly Zoroastrian state ideology than the Parthians had asserted. What survives suggests a Parthian religious landscape more syncretic than either its Achaemenid predecessor or Sasanian successor, absorbing Hellenistic astrological and iconographic conventions into a still recognizably Zoroastrian framework, a hybridity some scholars read as the empire's most distinctive religious contribution.