[1][2] The inhabitants of Sessa Aurunca venerate as patron saint their Bishop, St. Castus, a martyr at the end of the third century.

It is likely that Sessa Aurunca became the suffragan (subordinate) of Capua, when that diocese was raised to metropolitan status in 966 by Pope John XIII.

[5] It was certainly the case in March 1032, however, when Archbishop Atenulf of Capua consecrated Bishop Benedict of Sessa Aurunca, and confirmed him in the possession of the diocese, just as his predecessors had done.

In 1113 the seat of the bishop was transferred to a new cathedral in the center of the city, which was dedicated on 14 July to the Virgin Mary and Saint Peter.

[9] The cathedral is staffed and administered by a corporation, the Chapter, which is composed of four dignities (the Archdeacon, the Dean, and two Primicerii) and sixteen Canons.

The dioceses formerly members of the suppressed Province of Capua (Gaeta, Calvi and Teano, Caserta, and Sessa Arunca) became suffragans of Naples.