In the Gothic War (457-458) he was comes et magister utriusque militiae and together with Aegidius, he commanded the army of the Western Emperor, Majorian.
That same year Majorian started a military campaign to re-conquer Gaul; the army, reinforced by some barbarian mercenaries, dislodged the Visigoths of Theodoric II from Arelate and obliged them to return to their condition of foederati.
With the help of his renewed foederati, Majorian entered in the Rhone Valley, conquering its populations "some by arms and some by diplomacy".
[2] In 459, some envoys of Nepotianus and of the gothic comes Sunieric arrived in Gallaecia to announce the victory of Majorian and the treaty between the Romans and the Visigoths.
At the beginning of the 460s, Nepotianus was deposed by order of Theodoric II, maybe because he opposed the powerful magister militum Ricimer, and was substituted by Arborius.