[3] One 19th-century writer said that it was "one of the humblest ecclesiastical buildings in Anglesey", and that there were "no architectural features in this church worthy of delineation.

"[4] The date of the original foundation of a Christian building at this location is unclear, although one 19th-century writer said that it is supposed that a church was first established here in about 605.

[1] No part of a building from that period survives; the walls of the present structure have been said (by the 19th-century clergyman and antiquarian Harry Longueville Jones) to be "probably not older than the fifteenth century".

[6] St Peirio's is set in a churchyard in the countryside of Anglesey, by a road between Llanfechell and Bodewryd, to the north of the island, and is approached along a tree-lined path.

[3][5] In her history of Anglesey, published in 1833, the Welsh antiquarian Angharad Llwyd noted that the "small ancient edifice" was some distance from the village of Rhosbeirio, and that a service was only held in it on the third Sunday of the month.

[3] The 1937 survey by the Royal Commission on Ancient and Historical Monuments in Wales and Monmouthshire recorded that the church possessed a silver cup from 1630 and a salver dated 1784–85.