The site includes two churches and the base of a round tower. The larger church, with a nave and chancel, has been considerably altered, and has a complex building history (O'Keeffe, 2003). The internal measurements of the present nave are 41'4" x 18'8", and the chancel 26'9" x 16'2". It was originally a single-chamber church with antae at the E end, of which the N and E walls now form the N and E walls of the chancel. Foundations remain of a chancel which was added to the E of this. The original nave was made into a new chancel in the 15thc., and a new nave was built to the W of this (but possibly never completed). The chancel is barrel vaulted with a stairway to living quarters on the upper floor (probably added in the 15thc.). The nave has doorways at the W end of the N and S walls, and windows at the E end of the N and S walls. The chancel arch and N doorway incorporate re-used Romanesque fragments, and there are Romanesque fragments set around the S doorway, above the N window, and in the W window of the upper chamber.

The church was part of an early monastic site founded by St Mochoemog (d.655). Abbots are recorded in 752, 767, 900, 933, and 1014. The importance of the monastery decreased to manorial status at the end of the 12thc. Occupation appears to have continued into the medieval period.

The carved fragments built into the walls evidently came from a 12thc. building, but Leask (1946) argues that there is no trace at Liathmore of a building from which they might have come.

Leask (1946) argues that the jambs of the chancel arch are made up of voussoirs from an arch of large span, and suggests that the stones may come from one of the late 12thc. buildings of Holy Cross Abbey (nine or ten miles away), where the whole E arm was rebuilt in the 15thc. The only other building near Liathmore which was large enough to produce such stones is Kilcooly, but this was less drastically altered in the 15thc.