But beneath that Georgian order lies a much older, and largely vanished, history. The town sits on what were once the see lands of Glendalough, the great monastic site to the northeast, and at some point in the medieval period it functioned as an episcopal manor, meaning it was held and administered by a bishop, with a small borough attached to it.

Dunlavin surfaces in the historical record in 1326, when it appears in an Inquisition, a formal legal inquiry typically used to establish ownership or the extent of lands held by the crown or church. By that point the settlement already seems to have had some standing, but the documentary trail suggests it fell into decline not long afterwards. A mill is recorded in the fourteenth century, a detail that points to a functioning agricultural community rather than a purely administrative centre. The 17th-century parish church was demolished before 1838, leaving no visible trace of that earlier phase of the town's life. What a visitor sees today, then, is essentially a replacement settlement, built over or beside the bones of something much older and largely unrecoverable at ground level.