He was a son of King Godgisel, the Vandal king when his people breached the Rhine River frontier of the empire on the last day of 406. During that year, the Vandals had become heavily involved in a war with the Franks, who were already settled in Gaul as allies of the Romans, and who attempted to keep the Vandals out. Godgisel was killed in the fighting and Gunderic succeeded him.
Gunderic and his people ultimately crossed the Pyrenees Mountains into Spain, where Gunderic established himself in the part of Spain now known as Andalusia. It was then known as Vandalusia because it was ruled by the Vandals.
Around 426, the king of the Alans fell in battle against the Visigoths, and most of the surviving Alans appealed to Gunderic. Gunderic accepted their crown and thus became King of the Vandals and Alans.
Late in his reign, the Vandals themselves began to clash more and more with the Visigoths, often getting the worse of these battles because the Visigoths were so much more numerous. After Gunderic died early in 428, the Vandals elected his half-brother Geiseric as his successor, and Geiseric left Spain to the Visigoths in favor of invading Roman Africa.