During the 17th and 18th centuries, the Penal Laws placed many restrictions on Catholic worship. By the early 19th century most of these laws had either been repealed or fallen into disuse, and Catholics began to build churches in large numbers. At Lismore a new parish church was built in the 1880s, replacing an older and simpler building.

St Carthage's, Lismore, is largely the creation of Dublin-born Walter Doolin (1850-1902) and was erected between 1881 and 1884. The church contains some interesting stained glass of the Celtic Revival, notably a set of three windows commemorating saints associated with Lismore - Cathaldus, Carthage (with contemporary picture of the Castle) and Colman.

St Cartage's Parish Church was officially opened in 1884. It is seen as one of the finest examples of Lombardo-Romanesque churches in Ireland. Old red sandstone, quarried locally, and white limestone were used in the church's construction. The bell tower rises to a height of 120ft. above the richly detailed facade. A statue of St. Michael the Archangel, stands on a pedestal between the main doors. Above the doorway there is a mosaic of Christ the King, with the first and last letters of the Greek alphabet at either end of the arch over the mosaic. An arcade with statues of saints crowns the doorway. A rose window framed by the symbols of the apostles may be noted above this. A statue of St. Cartage stands in the alcove above the window. It is estimated that the church can accommodate up to 1,100 people. A short guide may be purchased inside the church with further information relating to the interior.