Building works were commenced and continued with slow progress, and the unfinished church was first used to hold Mass in 1842.

The parish church was elevated to pro-cathedral status in 1889, with the Bishop taking residence in Ennis.

In 1890, Thomas J. McRedmond became the Bishop of Killaloe, and decided to base the bishopric at the church in Ennis.

The cathedral was closed for six months in 1973, while work was undertaken to remodel the building to the requirements of the Second Vatican Council.

After a fire in the cathedral in 1995, the sanctuary was rebuilt and the interiors were redecorated, with works completed at the end of 1996.