He was the son of Shapur Mishanshah, a Sasanian prince who governed Maishan, and was the son of the Sassanian shah Shapur I. Hormizd's mother was Denag.
Hormizd's siblings were Hormizdag, Odabakht, Bahram, Shapur, Peroz, and Shapurdukhtak.
In 260, his father died and was probably succeeded by Denag as the governor of Maishan.
In 274, he was appointed as the governor of Sakastan and its surrounding regions.
Three years later, when his cousin Bahram II ascended the throne, Hormizd's sister Shapurdukhtak married the shah.