Built in 1839, Saint Mary's at Wallscourt follows a T-plan layout, a practical form that was common for Catholic churches in the decades following Catholic Emancipation, when congregations could finally build openly and with some ambition, though rarely with lavish funds. The result here is a gable-fronted building with a two-bay nave, single-bay transepts, and a canted apse, which is a polygonal rather than flat-ended recess at the west end, giving the interior a slightly more refined chancel. It sits close to the road through Kilreekil, visible from both directions, which gives it a civic weight that belies its relatively compact dimensions.

The craftsmanship concentrated at the entrance is worth particular attention. The bellcote, a small gabled structure for housing a bell, is cut and carved from limestone and sits above the east gable, while the pointed arch doorway below it has a chamfered limestone surround that shows careful tooling. These elements were clearly the work of experienced masons at a time when such skills were being deployed more widely on Catholic building projects across Ireland. Inside, the building accumulates detail across different periods: a later timber gallery was added at some point after the original construction, and the interior also contains carved marble altar furniture, leaded coloured glass windows, and decorative plasterwork on the ceiling of the apse. An open scissors truss, a roof structure in which paired rafters cross and brace each other in a scissor-like configuration, spans the nave overhead. A graveyard to the south of the building completes the site, grounding the church in the longer continuity of its community.