Sometime in the nineteenth century, the entire west gable wall was absorbed into a handball alley, the doorway bricked up and plastered over, and half of a fourteenth-century four-light tracery window buried behind the render along with it. The alley is long gone, but the doorway never reappeared. Visitors who eventually find their way inside must enter through a side passage in the north transept, the only route now available since the original entrance was sealed. It is a quietly disorienting beginning to a building that is, in almost every other respect, remarkably complete.

The priory dedicated to Saints Peter and Paul was founded in 1241 by Meiler de Birmingham, and sits on the east bank of the Clarin River in the north-east quarter of the medieval town, roughly 190 metres south of Athenry's castle. It attracted generous patronage from both Anglo-Norman and Gaelic lords throughout the medieval period, and a manuscript known as the Register of the Dominican Order of Athenry, now held in the British Museum, has allowed historians to trace its patrons and its structural growth with unusual precision. The church became a preferred burial place for de Birmingham's descendants and for several bishops of Clonfert and Kilmacduagh, and thirty friars were recorded here in 1445. The priory's later history was turbulent: granted to the Earl of Clanricard by Elizabeth I in 1568, then to the town of Athenry in 1574, it was sacked that same year by Clanricard's own sons. Friars returned in 1595, but the wars of the late sixteenth century damaged the buildings severely. The final indignity came in the eighteenth century, when the priory was gutted to furnish materials for a military barracks built immediately to its south. That barracks was itself subsequently demolished, and a terrace of houses occupies the ground today.

What survives is the church alone; no trace of the cloister or domestic ranges remains above ground. Yet the church itself is remarkably intact, its walls still standing to their original height across a nave and chancel measuring over 45 metres in length internally. The building accumulated layers across roughly three centuries: the nave and chancel from the initial 1241 construction, the northern aisle and transept added in the late thirteenth or early fourteenth century, and a tower inserted around 1425. That tower's insertion displaced an earlier altar, blocked the easternmost lancet window in the south wall, and encased the original circular arcade columns in later masonry. In the chancel, a triple-arched sedilia, a seat recessed into the wall for clergy during Mass, retains a carved head at one arch terminal that may represent a bishop. Ghosted in the east gable wall, the outline of an earlier and larger five-light window is visible behind the fifteenth or sixteenth-century replacement. The sacristy, accessed through a pointed doorway off the choir, now houses a collection of architectural fragments salvaged from elsewhere in the building, a small museum of removed and displaced stonework gathered into the one room that still has a roof over it.