The area had previously been the Diocese of Lilybaeum, but this was not reestablished and instead a new see established at Mazzara.

Of the bishops of Lilybaeum, the best known is Paschasinus, legate of Pope Leo I at the Council of Chalcedon (451).

[4] In 1093, Count Roger granted the territories forming the diocese of Mazara to Bishop Stephen and his successors, with permission of Pope Urban II.

[5] The first bishop of Mazara (1093) was Stefano de Ferro, a relative of Count Roger.

The Cathedral, dedicated to the Holy Savior, had a Chapter composed of four dignities and eighteen Canons.