Llanllawer church has a long and uncertain history. While there is no remaining physical evidence of an earlier church, historical records suggest it has medieval origins. There are records of it starting as a chapelry, but by the 1800s it was falling into disrepair. In the 1860s, London architect Mr. Withers and local builder Mr. James rebuilt the church we see today using local stone. The early medieval crosses they used in the rebuilding might have been found during the demolition of the earlier church. Recent archaeological surveys suggest the churchyard originally extended to the south.
In the neighbouring field stands a holy well, dating back to the medieval period. Covered by a stone and mortar well-chamber of unknown date, the entire structure was covered in earth until 1983 when it was removed, and the chamber walls repaired.
Within the church’s boundary are four early medieval stone carved crosses from between 1,200-1,000 years ago. Two are in the gateway to the churchyard and two are incorporated in the church building itself. Above the door in the north vestry, there is one with a linear Latin cross and radiating lines, one of only four examples in Wales. All these stones have been given scheduled monument status meaning they are protected because they are nationally important.