St. Tysilio's Church was, according to tradition, founded in the seventh century by St. Tysilio himself; this cannot be verified by any surviving early sources, but it is certain that an established church was on the site by the thirteenth century. Since its foundation, St. Tysilio's Church has been modified and added to on a number of occasions until the nineteenth century when the whole site was levelled and the building currently in situ was built in 1867 to the design of G.E. Street.
The church is in the Early English/ Early Decorated Gothic style, built primarily from green-grey Criggion stone with Cefn stone dressings with lancet windows. It comprises a nave with north aisle, inset chancel, organ chamber, vestry, south timber porch on stone plinth and round north-west tower with arcaded belfry and conical cap. There are few pre-nineteenth century remnants on the site; a stoup, eighteenth century wall tablets, a stone pillar sundial dated 1760, and a brass dated 1674.

Source: Cadw Listed Buildings Record
RCAHMW Inventory Documents

K Steele, RCAHMW, 24 November 2008