Rectangular church, 20.47 m x 7.16 m, roofless but with walls standing almost to full height. There is evidence of a smaller, earlier church in the massive masonry blocks in W and N walls, and an off-centre trabeated W doorway with inclined jambs. The church appears to have been extended to the E and S of the original structure in the early 13thc. It was originally 8.51 m wide at the E end. The S wall was later rebuilt N of its 13thc. position, narrowing the church and partially blocking an aumbry on the S side of the E wall. There are plain windows, one on the N and two on the S wall. A double window in the E wall has transitional sculpture. This is flanked by double aumbries, partially blocked on the S by the rebuilt S wall. A transitional doorway has been reset in the S wall.

An early monastic site with remains of St Sorney's Well and Bed. Fachtna Ó hAllgaith (d. 1232), coarb of Drumacoo, kept a guesthouse and a leper house (Gwynn and Hadcock, 1970, 34; AC 1232).

The doorway appears unusually narrow and some of the jointing is ill-fitting. Some of the voussoirs may have been removed and the imposts of the first order have been replaced with window mouldings. In the arch, only the second order has distinctively carved springers. The carving is of high quality, with fine detail and three-dimensional carving, and appears to belong to the later phase of the 'School of the West'. Leask compares the E window design to Corcomroe and the doorway to the E windows of Temple Jarlaith, Tuam. He compares some of the abacus mouldings to work of 1205-18 at Boyle, and some of the foliage designs to Cong, but the mouldings at Drumacoo appear more advanced than Boyle and the foliage is more deeply carved than at Cong. The dragon on the E capital of the first order of the doorway is similar to those on the chancel arch at Kilmacduagh, and the high relief beast heads on the second order are similar to that on that on the N nave arcade (NE angle, Pier 3) at Abbeyknockmoy. A row of beast heads with domed heads and almond shaped eyes is also found on the central capital of the E window at Kilfinaghta (Clare), on a shaft with a bobbin. Leask dates the doorway c.1235 on stylistic grounds, based on the similarity with Temple Jarlaith, Tuam. Kalkreuter dates the earliest parts of Drumacoo to c.1230 and the S doorway to c.1235.