A long rectangular church, 18.06 m x 7.39 m, built of rough blocks of granite with squared quoins. The gabled W and E walls remain to their full height of more than 9 m, and the N wall to its full height of c.5.5 m. The S wall is destroyed. At the W end part of the S wall has been rebuilt and a modern cross-wall blocks off the W end of the nave. Corbels along the nave walls would have supported an upper chamber, lit by a window in the W gable. 12thc. features include a flat-headed W doorway and two round-headed E windows with exterior labels supported by columns.

The monastery was founded by St Finian of Clonard in the early 6thc. The death of an abbot is recorded in 1017 and of an erenagh in 1050 (AFM). The building was in use as a Church of Ireland church until 1716/17.

The present church was probably built in the 12thc. Leask compares the door to that at Banagher (Derry), and dates it c.1100, but a date towards the mid or later 12thc. seems more likely. The framed E windows flanked by columns have no close parallels in Irish Romanesque.