These weathered stone walls may have begun life as St. Catherine’s friary, established by MacSwiny Bannagh for the Franciscan Third Order Regular, though what’s certain is that they were converted for Protestant worship after Killybegs became a borough in 1615. By 1622, the church was described as ‘newly re-edified and well repaired’, but like many religious buildings of its time, it suffered during the Confederate Wars when it may have sheltered friars fleeing from nearby Donegal.

The church underwent repairs around 1654-56 and continued serving the community throughout the 18th century before being abandoned in 1829 when the congregation moved to the newly built St. John’s Church. Today, the ruins reveal at least three distinct building phases: the main body likely dates from the 15th century, measuring 15.6m by 5.2m internally, whilst the north transept appears to be a 16th century addition. Later 17th and 18th century modifications include the arched transept gable, various window alterations and a western porch. The construction technique tells its own story; irregular rubble blocks with small pinnings form the walls, whilst rough ashlar quoins mark the corners, and several superimposed coats of plaster on the interior walls speak to generations of maintenance and care.

Architectural details throughout the structure offer glimpses into its evolution. The north transept, slightly askew from the main church body, features a double chamfered segment-headed arch with characteristic 16th century punch dressing. Original features include a blocked doorway in the south wall with a pointed head and wide chamfer, crowned by a chamfered hood-mould typical of 15th century craftsmanship. Various windows show evidence of being secondary insertions, some retaining their segmental heads and rear-arches, whilst others have been modified to accommodate timber frames. The building now rests within a graveyard, its walls still standing to full height despite centuries of abandonment, with ivy displacing quoins and trees growing through the masonry; nature slowly reclaiming what was once a focal point of community worship.