During the reign of Vologases I, Armenia turned into the main problem fueling the competition between the Arscasid (Parthian) Dynasty and the Roman Empire. The war between the two great powers over Armenia finally ended with the victory of Parthians, and the brother of the Parthian King was crowned as the King of Armenia. As a result, a branch of Parthian Dynasty was developed in this land. Following a historical researchmethod, the present study was mainly intended to explore the process of Iranian Parthians’ coming to power in Armenia and identify the determining factors
in this regard. The findings demonstrate that the Parthian branch in Armenia was formed under the influence of some external factors, such as competitions between Iran and Rome, and certain internal factors, such as the interestof Armenian aristocrats and public in Parthians.