Built between 1829-34 by John Leeson with later work by Patrick Byrne in 1858, St Nicholas is the only church in the city to preserve its two sets of communion rails intact. Originaly the church provided a much more stern aspect to the street as its portico and campanile were added in 1860 by John Bourke. The church is set back from the street facing onto a small courtyard entered by some simple gates.

The internal space of the church is dominated by the 'Pieta' by John Hogan above an neoclassical Italian altar flanked by angels. It is believed he may also have been responsible for the side altars. Patrick Bryne during his alterations, closed up the windows around the 'pieta' for dramatic effect. There is also stained glass from the Harry Clarke Studio dating from 1928 and statuary by John Smith.