The youngest son of Shapur I (), Narseh served as the governor of Sakastan, Hind and Turan under his father. Shapur I was eventually succeeded by his son Hormizd I (), who died after a reign of one year. Shapur I's eldest son Bahram I, who had never been considered as a candidate for succession to the throne by his father, ascended the throne with the aid of the powerful Zoroastrian priest Kartir. He then made a settlement with Narseh to give up his entitlement to the throne in return for the governorship of the important frontier province of Armenia, which was a persistent cause for war between the Roman and Sasanian Empires. Narseh held the title of "Vazurg Šāh Arminān" ("Great King of Armenia"), which was used by the heir to the throne in the early Sasanian times. Nevertheless, Narseh most likely still viewed Bahram I as a usurper.