This site beside the river Ceidiog has probably been used for worship since early medieval times, and perhaps even before Christianity came to Wales. Some have speculated that St Trillo founded a Christian establishment here in the 6th century, after wandering inland from the cell which he reputedly built at what is now Rhos-on-Sea.
The church was recorded in 1254 as Ecc’a de Lantreullo. The old church was replaced in 1776. The new structure was low and included a tower, but its foundations proved defective. By the 1870s the building was so badly cracked that most of the structure was rebuilt, largely on the same footprint. The walls of the nave, up to the windows, were retained, as was the lower part of the tower. The new church was designed by Samuel Pountney Smith, of Shrewsbury.
In 1960 a stone with an ancient inscription was moved to the church from nearby Blaen y Cwm. The six-line text is too indistinct to be read clearly, although some believe it includes Trinitatis (Trinity). Also in 1960, at the Archdeacon’s insistence, the church’s old font, dating from c.1530, was moved back into the church from the Victorian vicarage – where it was a flowerpot!
Several memorials at the church relate to the ancient Lloyd family of Hendwr, ancestors of Owain Tudur, grandfather of King Henry VII. Another family member, Dafydd ab Ifan ab Einion, held Harlech Castle for the House of Lancaster from 1460 to 1468, during the Wars of the Roses.
In the churchyard is the canopied tomb of Katherine Wynne, who came from the Royalist Bulkeley family of Anglesey. Her second husband was Richard Wynn, also from a powerful North Wales family. They married in 1661, soon after the monarchy had been restored, and lived at Branas Uchaf, near Llandrillo.