In the current research, the basis of the work is based on archaeological evidence related to diplomatic etiquette and protocol (inscriptions) and other sources (written or oral literature) available from Achaemenid to Sassanid era. Based on this, a collection of diplomatic rituals was compiled, and based on these sources it was determined that at least some diplomatic rituals existed in the ceremonial customs of Iranian courts from the beginning and continued, including the custom of covering the face of the ruler/king from his guests and subordinates and the tradition of receiving or giving offerings and gifts. But some other customs have gradually emerged or undergone transformations for greater efficiency, including the custom of welcoming and accompanying delegations from the border to the royal residence. The combination of these customs and traditions from the beginning to the end of the period in question and their consistency and dynamism have formed the diplomatic ceremonies of ancient Iran.