Of all the Cistercian houses founded in Wales, Cymmer was probably the smallest and poorest, despite it being located on an important thoroughfare during the middle ages.

In 1197 a small group of monks left Abbey Cwmhir and traveled north west across the Cambrian mountains to the head of the Mawddach estuary. It was a perilous journey which resulted in the death of a few of the the deeply religious men, however having founded the Abbey in 1198 they were grateful for the patronage of Maredudd ap Cynan, a grandson of Owain Gwynedd, for it allowed them to breed sheep on the surrounding hills. The Monks were also involved in mining and metallurgy.

The Abbey was among those that suffered quite severely during the various Welsh wars, in fact it sustained heavy damage during the war of 1282/3 and received £80 in compensation following Edward Ist conquest of Wales. Following the war its economic position declined even further. However, it did possess a very large and fine silver gilt chalice and paten, which must have been hidden on the mountainside at the Dissolution of the monasteries by Henry VIII. They were rediscovered in the 19th century and are now in the National Museum of Wales.

Because the Abbey suffered severe financial difficulties it may account for the fact that it was never completed. The small, plain, rectangular church was originally intended as the nave only of a much grander building scheme that was apparently abandoned.

Following the Dissolution in 1537, Cymmer was left to deteriorate for nearly 400 years and, apart from ground level foundations, the fragmented rubble walls of the abbey church are all that have survived. Encompassed within a farm today, some of the claustral range having been converted to provide storage sheds and shelter for livestock; indeed the farmhouse is believed to have been part of the abbot's accommodation and guest house.

Although Cymmer Abbey was not an important house in medieval times, it certainly has a haunting timelessness about it today. The austerity, the tranquility and the remoteness can easily conjure up monastic scenes from the 14th century.