As far back as 1291 Llandrindod is referred to by two names, Lando and Lanvayloir (a misprint for Llanfaelog). Lando is a form of the modern Welsh Llandduw, which may stand for the Llan (Church) of God, or possibly for Llan + Dewi (Saint David.) Llanfaeolog refers the Church to the name of the local Welsh Saint, Maelog. Llandrindod itself means Church of the Holy Trinity. From the sixteenth century there are suggestions that a rudimentary school was run in the building (or its porch).

The current Church was built by the Victorians on the original site, the craggy hilltop lending itself to a prominent building. The Church stands 867 feet above sea level. Nothing remains of the early Churches here—probably going back to the Celtic Saints, like Maelog and Dewi (David).—as these would almost certainly have been built of wood and thatch rather than stone.

In 1893, the Rector of Llandrindod, Archdeacon Henry De Winton, is said to have had Llandrindod and Cefnllys Churches unroofed, in an attempt (it is said) to force people to attend the new Church (known as Holy Trinity) which had been built in the centre of Llandrindod Wells. The Church was, howver, rebuilt in 1894 by Nicholson & Sons. There is disagreement about the story of the roof, some believing that the roof collapsed due to old age.

The earlier Church on the site was levelled but the foundations can be seen at the base of the East wall, and further influenced the alignment of the new building. In 1911 it was extended to the west with the addition of another bay, a new vestry and a heating chamber. Some records have suggested that a baptistery was added, also in 1911, but if so, it is unclear exactly where.

In the work of restoration at the end of the 19th century a curious carved stone with fertility symbolism - a sheela-na-gig was unearthed from the floor of the Old Parish Church. It is a fine example of such a stone and is now on loan to the Radnorshire Museum by the Metropole Hotel.

The Church is also important as the place where the very first Archbishop of Wales was elected in 1920. A plaque records this event. It reads Within these walls on Wednesday April 7th, 1920, Alfred George, Bishop of St Asaph was elected First Archbishop and Metropolitan of the Church in Wales’. This election still takes place in Llandrindod, but now happens in Holy Trinity.