In the 1220’s, Dunmore was given by the De Burghs family to Meilor de Bermingham, where it was held by him and his heir until the 1650’s.
In 1225, de Bermingham built his first castle here, however it was burnt to the ground by the sons of the Kings of Connacht, Fichra O’Flynn in 1249 and by Rory O’Connor in 1315.
It is believed that the ruins of the current Dunmore castle were probably built after the last burning. The castle was a tower house consisting of four storeys and situated on a motte with the remains of a fortifying wall around it.
The castle was believed to have been at one stage taken by Sir Henry Sidney, but it remained in de Bermingham hands until the Cromwellian plantations. The castle although in ruins, is still well preserved with many features of the castle still visible.