Llandecwyn is dedicated to St. Tecwyn, who founded this church in the 6th century AD. Although the current church on the site was built during Victorian times, it is set in a graveyard, dating back to at least the time of Tecwyn, and is located on an ancient pathway that was used possibly as far back as neolithic times. The churchyard is circular, as was typical for churches of that time period, and includes a lychgate.
Within the church is a stone dating to the 11th century. It is inscribed with a cross and dedicated to St. Tecwyn.
Llandecwyn is the only church in the region not on the coast, and is located, instead, at an elevation of 150 meters above the Dwyryd estuary, with amazing views of the surrounding area.
Tecwyn appears to have been the son of Ithel Haul of Brittany, and brother to other famous saints, including Tanwg, Twrog, Tegai and Baglan, all of whom were saints who founded churches in Gwynedd. According to legend, these brothers arrived in Wales in the company of St. Cadfan to reinvigorate Christianity in Britain.
At one time, there was a thriving community at Llandecwyn, but the church now stands alone.