The building on St Macdara's Island measures just 4.47 metres long and 3.43 metres wide, yet its architectural ambition is plain: a stone-flagged roof, projecting antae (the sidewall extensions that reach upward past the gable ends, a feature borrowed from timber-building traditions and translated into stone), a trabeate west doorway with a flat horizontal lintel rather than an arch, and windows of differing shapes in the east and south walls. The finial crowning the roof ridge is a reproduction; the original was recovered in 1884 but has since gone missing, which gives the restored monument a quietly poignant quality, a copy standing in for something real that no longer exists.

The church sits at the south-eastern end of Cruach na Cara, the island's Irish name, and was founded by St Sinach Mac Dara, the figure from whom the island takes its more familiar designation. Around the church the early medieval monastic landscape is still legible, if you know what you are looking at. Leachta are low, rectangular stone cairns associated with commemorative prayer, and several survive here alongside cross-slabs, carved stone crosses, and clochans, the small dry-stone beehive cells in which monks once lived and slept. Beside the east gable, a rectangular area defined by boulders and a single slab, roughly 1.8 metres by 0.82 metres, is identified by tradition as the saint's bed. Earlier surveys, including a plan published by F. J. Bigger in 1896 and a sketch recorded in the Ordnance Survey Letters, showed flanking walls to the north and south of this feature; none of those walls survives today.

The island is accessible only by boat from the South Connemara coast, which means the site receives far fewer visitors than its architectural significance might otherwise attract. The church is a restored National Monument, so the fabric has been stabilised, but the surrounding scatter of leachta, cross-slabs, and clochan foundations remains exposed to the elements and underfoot in the grass. Fishermen from the region have long observed a tradition of dipping their sails three times in salute when passing the island, a custom that speaks to how deeply the saint's memory is woven into the working life of this stretch of Atlantic coastline.