A single cell church (12.95 m x 6.7 m), faced externally with fine jointed ashlar. The only original opening to survive is a plain, recessed, S window with an arcuated lintel (height 0.63, width 0.30 m). Romanesque sculpture is found on a small carved relief on the N wall.

Close by the church is a house-shaped shrine known as St Tigernach’s Shrine. This is oriented EW, aligning with the doorway of the adjacent round tower. A high cross (not Romanesque) is also associated with this site.

A monastery was founded at Clones in the 6thc. by St Tigernach. The deaths of ensuing Abbots and bishop are recorded in the Annals, as is the burning of the monastery in 1095. In 1139 Cathal MacMaelfhinn, successor of Tigernach, died. The monastery probably became an Arrosian foundation after 1140. The town and abbey were burned by Hugh de Lacey in 1207 and both were rebuilt by the Anglo-Normans. In the 16thc. the abbey and monastic buildings, all in a ruinous state, were given to Henry Drake. According to 19thc. accounts, members of the MacMahon family were interred in a vault beneath St Tigernach's stone shrine.

The church is one of a handful of Irish Romanesque buildings to be faced in ashlar, suggesting that it was a structure of particularly high status. The placing of a relief carving of any nature on an external wall is not paralleled elsewhere in Ireland. It is possible that the stone may originally have been carved for other purposes, and reused in this location, when good quality ashlar was being sought for the facing of the church.

The tomb shrine at Clones is comparable to a number of other shrines in Ulster, at Banagher, Bovevagh and Saul, but is the only monolithic example. The shrine was probably erected as a focal point for the cult of St Tigernach, and the small vault beneath it may originally have held his relics. The form of the shrine is based closely on metalwork models, and in this respect it may be paralleled with Romanesque high crosses such as the market crosses at Glendalough (Wicklow) and Tuam (Galway), both of which appear influenced by German examples in their form. The origin of the Clones model is uncertain, although the finials are of a type common to insular metalwork shrines, (such examples may be found in the Musée des Antiquités Nationales, St Germain-en-Laye, France). The similarity of the gable figure to a carved ecclesiastical figure from Aghalurcher (now in the Fermanagh County Museum), suggests a native tradition.

Harbison (1999) has identified some low relief carving on the roof of the shrine as scenes from the Life of St Tigernach, but these are so worn it is difficult to interpret them with any certainty.