The patron saint of the diocese of Kilmore is St. Felim who lived in the 6th century. Little is known about him except that he is said to have founded a church at Kilmore near Cavan, which subsequently gave its name to the diocese.
Bishop Andrew McBrady (1445-55) rebuilt the ancient church and received permission from Pope Nicholas V to raise it to the status of a cathedral. The cathedral was confiscated as a result of the Reformation and the diocese had no cathedral for 300 years.
There was, in the middle of the 18th century, a Mass house in Killynebber to the right of the lane leading to Annagelliff, near Cavan Town. In 1774 a new chapel was built at ‘Skelton’s Ford’, which later became the site of the old cathedral. In 1823 this chapel was rebuilt and slated while Fr. Patrick O’Reilly, a native of Killann parish, was parish priest. In 1862, Bishop James Browne had the Cavan parish church extended and it became the cathedral of the diocese of Kilmore and it was dedicated to St. Patrick.
The present Cathedral of Saint Patrick and Saint Felim was built between 1938 and 1942 during the episcopacy of Bishop Patrick Lyons. The architect was W.H. Byrne & Son and the contractor was John Sisk & Son. It was dedicated on 27 September 1942 and consecrated on 14 September 1947. It cost £209,000 to build.
The cathedral is neo-classical in style with a single spire rising to 230 feet. The portico consists of a tympanum supported by four massive columns of Portland stone with Corinthian caps. The tympanum figures of Christ, St. Patrick and St. Felim were executed by the Dublin sculptor Edward Smith.
The 28 columns in the cathedral, the pulpit and all the statues are of Pavinazetto marble and came from the firm of Dinelli Figli of Pietrasanta in Italy. The fine work of George Collie can be seen in the Stations of the Cross and in the mural of the risen Christ on the wall of the apse. Directly above the mural are 12 small stained glass windows from the Early studios showing the heads of the twelve apostles. The high altar is of green Connemara marble and pink Middleton marble while the altar rails are of white Carrara marble.
The apse has two side chapels on the north and two on the south. The Blessed Sacrament is now reserved in the north chapel closest to the altar. The six splendid stained glass windows in the nave and the one in the south transept come from the studios of Harry Clarke. They were added in 1994.