The church is located in sand dunes, about 20m from the high water mark of St George's Channel,[a] at the southern end of the village of Llandanwg.

[5] The current building is medieval, with the western end possibly dating back to the 13th century.

[7] However, the presence of 6th century inscribed stones, and the dedication to St Tanwg, suggest much earlier use of the site as a church, possibly dating to around 453 AD as part of Saint Patrick's work to establish links between Ireland and Britain.

[10] The floor of the church was flagged in 1786 and, three years later, some medieval paintings were lost during replastering and repainting of the walls.

[3][4][5] The old church was abandoned, and the 15th century octagonal font, bell[c] and other furnishings, removed to the new building.

[11] In 1884 the church was re-roofed for £80 by the Society for the Protection of Ancient Buildings, who had raised an appeal for funds.