In 314 Epictetus, its bishop, was present at the Council of Arles. Another Epictetus, Bishop of Centumcellæ towards the middle of the fourth century, was an Arian and a counsellor of Emperor Constantius.
In 1854 the union with Santa Rufina was severed and Civitavecchia was united with the diocese of Corneto. No bishops of Corneto are known for the ancient Christian period; it was made a diocese in 1435. Until 1986 the united diocese was known as Tarquinia e Civitaveccia .