Zoroastrianism only enters recorded history in the mid-5th century BCE. Herodotus' The Histories includes a description of Greater Iranian society with what may be recognizably Zoroastrian features, including exposure of the dead.
According to Herodotus i.101, the Magi were the sixth tribe of the Medians (until the unification of the Persian empire under Cyrus the Great, all Iranians were referred to as Mede or Mada by the peoples of the Ancient World), who appear to have been the priestly caste of the Mesopotamian-influenced branch of Zoroastrianism today known as Zurvanism, and who wielded considerable influence at the courts of the Median emperors.
Following the unification of the Median and Persian empires in 550 BCE Cyrus II and later his son Cambyses II curtailed the powers of the Magi after they had attempted to seed dissent following their loss of influence. In 522 BCE the Magi revolted and set up a rival claimant to the throne. The usurper, pretending to be Cyrus' younger son Smerdis, took power shortly thereafter. Owing to the despotic rule of Cambyses and his long absence in Egypt, "the whole people, Persians, Medes and all the other nations" acknowledged the usurper, especially as he granted a remission of taxes for three years.
According to the Behistun Inscription pseudo-Smerdis ruled for seven months before being overthrown by Darius I in 521 BCE. The "Magi", though persecuted, continued to exist. A year following the death of the first pseudo-Smerdis, named Gaumata, a second pseudo-Smerdis, named Vahyazdāta attempted a coup. The coup, though initially successful, failed.
Whether Cyrus II was a Zoroastrian is subject to debate. It became the non-imposing religion of his empire, and its beliefs would later allow Cyrus to free the Jews from captivity and allow them to return to Judea when the emperor took Babylon in 539 BCE. Darius I was certainly a devotee of Ahura Mazda, as attested to several times in the Behistun inscription. But whether he was a follower of Zoroaster has not been conclusively established, since devotion to Ahura Mazda was (at the time) not necessarily an indication of an adherence to Zoroaster's teaching.
Darius I and later Achaemenid emperors appear to have permitted religions to coexist. Nonetheless, it was during the Achaemenid period that Zoroastrianism gained momentum. It was also during the later Achaemenid era that many of the divinities and divine concepts of proto-Indo-Iranian religion(s) were incorporated in Zoroastrianism, in particular those to whom the days of the month of the Zoroastrian calendar are dedicated.
Almost nothing is known of the status of Zoroastrianism under the Seleucids and Parthians who ruled over Persia following Alexander the Great's invasion in 330 BCE. According to later Zoroastrian legend, many sacred texts were lost when Alexander's troops invaded Persepolis and subsequently destroyed the royal library there. Diodorus Siculus's Bibliotheca historia completed c. 60 BCE, which is to a great extent an encapsulation of earlier works, appears to substantiate Zoroastrian legend (Diod. 17.72.2–17.72.6). According to one archaeological examination, the ruins of the palace of Xerxes bear traces of having been burned.