It was built in 1434 by the will of King Alfonso d’Aragona following the victory over the troops of Louis III d’Anjou, an event that Piaggia believes invented. Dedicated to Saint James Apostle Patron of Spain, still maintains its original structure fifteenth century. It was the Mother Church of the city until 1616, when the Cathedral was inaugurated, built inside the Castle.
With a sober Renaissance appearance not altered by the subsequent inserts, it has a single-order facade sealed by stone cantons and crowned by a triangular attic with clock and stucco; the door, of seventeenth-century taste, is adorned with slender Corinthian columns and surmounted by a niche with the statuette of the titular saint, all decorated with volutes and torciglioni: the inscription dates from 1712. The simple rectangular window is adorned with modest friezes. The secondary door on Via Medici is flanked by elegant Doric parastes on a decorated base and with a broken tympanum enclosing the inscription: a folder decorated with volutes bears the dedication to the titular saint.
On the side of the Marina there is another opening and the sacristy with a slender neo-Gothic portal. Inside, in 1609, the original wooden ceiling was replaced by a barrel vault. It has a single rectangular nave with a large quadrangular choir connected by the triumphal arch, adorned with the civic coat of arms and decorated with putti in stucco that raise a veil.
There are four side altars dedicated to the Souls of Purgatory, Saint John the Apostle, the Annunciation and the Crucifix.
Some paintings of the eighteenth century attributed to Scipio Manni and depicting the Crucifixion, the Annunciation and the Mass of San Gregorio; other paintings that we find in the choir area are the death of Sant’Andrea d’Avellino, San Nicola (1804), Sant’Antonio Abate and the Probatica Pool (1785). The baptismal font and the wall case of the Holy Oil date from 1626, while the floor dates from 1777. At the centre of the vault is a fresco from 1761 depicting The Trial and Martyrdom of Saint James. The high altar of the seventeenth century is that of the old cathedral to the castle, moved here in 1866 to replace an ancient wooden altar. In the entrance there is the modest monument Zirilli Proto of 1862. Finally it is necessary to remember the presence of the seventeenth-century crypt below the area of the presbytery where were buried the remains of numerous Garibaldi fighters of July 20, 1860 and the patriot Milazzese Matteo Nardi, moved in 1864 in the large ossuary of the old cemetery of San Giovanni. There is also a hole marked by a circle and a date, 25 July 1943, which recalls the miraculous safety of the temple during the Anglo – American bombardments when a bomb hit the roof and fell unexploded at the foot of the statue of Santo Stefano Protomartire.