[5] Killashee traces its foundation to the 5th century and is associated with Auxilius, a nephew and companion of Saint Patrick, with the Annals of the Four Masters dating its founding to AD 454.

In the mid-19th century the Moore family owned Killashee and built a large Victorian mansion; this was in 1927 sold to the Holy Union Sisters for a convent and is today a hotel.

The Ordnance Survey reported that "a few years ago an old castle stood near the Round Tower" but that it had been thrown down and that "the stones of it are yet to be seen.

[9] It is incorporated into the fabric of the church in an unusual manner, with St Kevin's Kitchen in Glendalough being the most similar.

[14] There is a graveyard surrounding the tower and church, and a holy well dedicated to Saint Patrick located nearby.