The Cathedral is the fourth church to be built on this site. The first one recorded was a Carmelite church built in the early fourteenth century. After the dissolution of the monasteries in the 1530’s it fell into disrepair. The second church, known as the Matthew Chapel was built around the mid eighteenth century under the partronage of George Matthew who lived in Thurles at the time. The third church built on the site was known as the ‘Big Chapel’ and was dedicated to Saint Patrick. This church was a spacious, T-shaped building built between 1807-1808 at a cost of £10,000. The big chapel served as the Cathedral until the early 1860’s.

The fourth Church built here is the present Cathedral. Work began on it in 1861. Dr. Patrick Leahy who was Archbishop at the time decided to replace the ‘Big Chapel’ with a more grandiose structure. He regarded the ‘Big Chapel’ as “not worthy of this great diocese much less to be the metropolitan church of Munster”. Dr. Leahy loved all things Roman: chant, Roman ceremonies and buildings. The Archbishop engaged the well-known and established church architect of the day, J.J. McCarthy, who abandoned his normal Gothic revival style to accommodate Dr. Leahy’s preference. So McCarthy used an Italianate Romanesque style. The Cathedral is modelled on the Cathedral of Pisa in Northern Italy. The foundation stone was laid in 1865 and by 1870 it was roofed and the work began on the interior. The consecration was performed by Dr. Leahy’s successor, Dr. Thomas Croke on 22nd June 1879. The total cost of construction of the Cathedral was £30,000. The bulk of the finance came from within the Diocese and the debt was cleared by its completion. Dr. Leahy was a skillful fundraiser. He levied each parish according to its ability to pay thus maximizing the return from the diocese. Dr. Leahy visited every Church in the Dioceses seeking support for the Cathedral and he also sent collectors abroad to Canada, America and England to tap the Irish in these countries.