Church Island takes its title from the fragmentary remains of a rectangular church on its south-eastern shore, a building now reduced to very poor condition, its walls of uncoursed limestone rubble barely legible against the surrounding enclosure. What survives of the east wall retains a single-light window, a lone opening that once admitted light to whatever interior life the building once held.

The church sits within a stone enclosure, the kind of bounded sacred space common to early and medieval Irish ecclesiastical sites, where a low wall would have demarcated the consecrated ground from the ordinary landscape beyond. The structure itself was built from uncoursed limestone rubble, meaning the stones were laid without the regular horizontal rows of dressed masonry; a modest technique suited to rural insular sites where elaborate quarrying and cutting were neither practical nor necessary. The island is reached from the mainland by a stone causeway, which suggests the site was considered worth the effort of permanent access, even if what now remains gives little indication of its original scale or purpose.