The medieval nave and chancel were not demolished when the building was remodelled in the nineteenth century; they were absorbed, rotated in function, and made to serve as a south aisle for the new church. Walk along the south wall and you are walking beside the oldest surviving stonework on the site, a wall that once faced the cloister garth and still holds a cusped twin-light pointed window with an elongated quatrefoil above the lights, and below it an ogee-headed piscina, a small stone basin used for washing liturgical vessels, set into the wall at its original medieval height.

The monastery was founded by Geoffrey de Marisco before 1226, according to Gwynn and Hadcock, and belonged to the Trinitarians, an order established in the twelfth century primarily for the ransoming of Christian captives held in North Africa and the Holy Land. In the taxation of 1302 to 1306 the house was valued at 40 shillings. It was dissolved in 1539 and by 1595 had passed into the hands of Sir Henry Wallop. The building sat in varying states of ruin until 1811, when the earl of Dunraven had it reconstructed for use as a Roman Catholic parish church. Most of what a visitor sees today in terms of doors, windows, and dressed stonework is the result of that reconstruction, with the masonry largely rough-coursed limestone rubble. The crossing tower, however, retains considerable medieval complexity: it rises on plain rectangular piers, is covered by a quadripartite vault, and contains spiral stairs, mural chambers with pointed vaults, and a small projecting turret at the south-east angle that includes a garderobe, a medieval built-in latrine.

The building is an active parish church and is generally accessible during normal opening hours, though visitors interested in the medieval fabric should focus attention on the south wall of the nave and on the crossing tower, which is the most structurally elaborate surviving element. The north range of the original cloister buildings, a cloister being the covered walkway and ranges of domestic rooms that surrounded a central courtyard in a monastic complex, appears to have been incorporated into later school buildings to the north, with two towers at either end of the range still partially legible. There is also a refurbished dovecot at the north-west corner of the church grounds, easy to overlook but worth a moment. Adare itself has several other medieval ecclesiastical remains within a short distance, and the Trinitarian church is best understood alongside them rather than in isolation.