It is not known when Cassano became an episcopal See. Some place the establishment in the 5th century, though without supporting evidence. In 859 Cassano and Cosenza were the headquarters of the Gastaldates of the Lombards of the Duchy of Benevento. In their turn the Lombards were attacked again and again, as were the Greeks in south Italy, by the Saracens. The Greeks were able to drive the Saracens away, and reorganized Calabria as part of the Greek Empire and the Greek Church of Constantinople. Cassano was established around this time as a suffragan diocese of the Greek Metropolitan of Reggio Calabria. In 1059 mention is made of a bishop of Cassano, whose name is not reported. He was engaged, along with the Provost of Gerace, in resisting the advance of the Normans, led by Robert Guiscard and his brothers. A battle took place against Count Roger at San Martino in Valle Salinarum, in which the Greeks, led by the bishop of Cassano, were defeated. In 1096 we read of a bishop of Cassano known as Saxo, who was a Vicar of Pope Urban II and Pope Paschal II in the region. In the 11th Century, the Diocese became a Suffragan of Reggio Calabria. Pope Paschal II, however, granted the Church of Cassano complete immunity from the jurisdiction of the Metropolitanate of Reggio Calabria, and took it directly under the protection of the Holy See. On 20 October 1144, King Roger II of Sicily confirmed the privileges of the Church of Cassano. On February 13, 1919, the Diocese had territory transferred to create the Eparchy of Lungro for the Italo-Albanian Catholic Church. On January 30, 2001, the Archdiocese of Cosenza-Bisignano was elevated to a Metropolitan See with Cassano all'Jonio as a suffragan diocese.
Seminary
In accordance with the decrees of the Council of Trent, Bishop Serbelloni appointed a committee to plan the creation of a seminary for the diocese of Cassano. The seminary was formally created by a decree of Bishop Carafa on 6 March 1588, and in 1593 Bishop Audoeno fixed the number of scholars at twelve, and for the next century the number never exceeded twenty. The seminary was perpetually short of funds.
Cathedral
The old cathedral was consecrated by Bishop Tomacelli on 3 May 1491. The bell tower was completed by Bishop Gaetano in 1608. The new cathedral was consecrated on 22 March 1722 by Bishop Francesco Maria Loyerio of Umbriatico. The decoration of the Choir was completed in 1750. The stucco façade of the cathedral was completed by Bishop Coppola in 1795, and the marble pulpit installed. Many of the treasures of the cathedral were stolen or damaged during the revolutionary period 1798–1806. The Cathedral was governed by a Chapter, composed of four dignities and eighteen Canons. The dignities were: the Archdeacon, the Dean, the Cantor and the Treasurer.
