The church at Boyle is one of the outstanding examples of Romanesque architecture in the country. It follows the so-called Fontenay plan, with a square presbytery flanked by two chapels in each arm of the transept. The church is well-preserved, though the walls of both nave aisles have been destroyed. The nave of eight bays has an unusual variety of pier forms: four Romanesque drum piers, eight shafted clustered piers, an octagonal pier, and six rectangular piers with triple shafts on the E and W faces. Scattered throughout the building there is an array of carved corbels, the majority furnished with some species of foliage ornament.

Little survives of the claustral buildings and there are no remains of the cloister arcades.

The sculpture is executed in a hard wearing sandstone, grey and yellow in colour, which was quarried locally.

The monastery at Boyle was founded in 1161 as a daughter house of Mellifont. The founding community in fact left Mellifont thirteen years earlier, trying out two other sites before eventually settling beside the river Boyle. The major benefactors were evidently the local kings of Moylurg. Construction began soon after the foundation, and, according to the annals, the church was consecrated in 1218 or 1220.

Following the dissolution, the monastery fell into disrepair; the buildings were used as a barracks in the seventeenth century, by which time the cloister arcades and most of the conventual buildings had been destroyed. At some unknown period (seventeenth or eighteenth century?) four massive buttresses were erected on the site of the N aisle, a strategy designed to prevent the collapse of the N elevation of the nave. During the early 1980s limited excavation took place in the area of the N walk of the cloister, revealing a substantial drain.

No other Irish church can provide such an instructive sequence of sculpture as that at Boyle. Covering a period of approximately fifty years, the carvings of the abbey are fundamental to the development of Romanesque W of the Shannon. The earliest carving in the building - a stunning animal head on the angle of the sedilia - has close parallels with those on the W doorway of the Nuns' church at Clonmacnois (1167). It is almost certainly by the same hand. This not only confirms a date of c1165-70 for the earliest work at Boyle, but illustrates the fact that masons working in local Romanesque techniques were employed by the Cistercians. There are related sculptures at Kilmore (Cavan) and Clonfert. Transport along the river Shannon and its tributaries no doubt helps to explain these connections. Other carving at the E end, most notably the 'hidden' face in the N chapel of the N transept, is executed in the relatively shallow relief technique favoured by Hiberno-Romanesque sculptors. This latter capital, with its two tiny pelta designs, has a distinctly Celtic flavour.

Most of the early work consists of varieties of scalloped and foliate designs, some of the latter ultimately derived from classical acanthus. The broad, plain leaves found on two capitals in the N transept, are Cistercian type, originating in Burgundy and much used in England. The 'split scalloped' motif found in the crossing capitals, re-appears at Abbeyknockmoy. It appears to have an English background (cf Lilleshall, Shropshire).

The capitals of the three clustered piers of the N arcade represent a new departure. Although the designs employed, especially the hanging trefoiled leaf, are commonplace in Romanesque art, the exact antecedents remain unclear. Some features of the capitals recall the more sophisticated foliage capitals in the triforium of the S transept of Christ Church, Dublin, and a date of c1190-1200 is likely.

The most extensive amount of carving in the abbey was carried out by a sculptor dubbed (by Stalley in 1971) as the 'Ballintober master'. This sculptor and his workshop executed the capitals of the last four bays of the nave, as well as the corbels inserted in the spandrels of the arches. While most of the capitals are covered with dense patterns of palmette foliage, there are a few instances of animals and human beings. The so-called dogs and chickens capital in the S arcade is one of the outstanding works of Irish Romanesque: a complex composition, executed with plenty of vigour and depth. The sculptor can be recognised through a number of personal details, such as the furled leaf with a line of berries at the edge of the leaf, or the animals, which sprout foliage tails. The workshop was employed at Ballintober Abbey between 1216 and 1225, suggesting that the sculpture at Boyle was executed just before the consecration of 1218/20. The sculptor also worked at Abbeyknockmoy (founded 1190), a daughter house of Boyle, and the impact of his foliage designs can be seen in several other churches of Connacht, most notably that at Cong. The sculptor combined both local features with knowledge of more cosmopolitan Romanesque and it is a pity that the precise background of this imaginative and skilful artist remains unclear.