The main façade, connected with arcades to the Archbishops' Palace

The church was erected in 1185 by Walter Ophamil, the Norman archbishop of Palermo and King William II's minister, on the area of an earlier Byzantine basilica. By all accounts this earlier church was founded by Pope Gregory I and was later turned into a mosque by the Arabs after their conquest of the city in the 9th century. Ophamil is buried in a sarcophagus in the church's crypt. The medieval edifice had a basilica plan with three apses, of which only some minor architectural elements survive today.

The upper orders of the corner towers were built between the 14th and the 15th centuries, while in the early Renaissance period the southern porch was added. The present neoclassical appearance dates from the work carried out over the two decades 1781 to 1801, supervised by Ferdinando Fuga and Giuseppe Venanzio Marvuglia. During this period the great retable by Gagini, decorated with statues, friezes and reliefs, was destroyed and the sculptures moved to different parts of the basilica. Also by Fuga are the great dome emerging from the main body of the building, and the smaller domes covering the aisles' ceilings.