It was built around the beginning of the twelfth century as a motte and bailey castle and this was probably replaced mid-century by a stone shell keep.

Tretower (Welsh: Castell Tretŵr[1]) was founded as a motte and bailey castle by Picard, a follower of Bernard de Neufmarché.

By about 1230 a tall cylindrical keep was added to the inside of the shell keep, possibly by his great-grandson, Roger Picard II, and the space between was roofed over.

In the early 14th century residential buildings were constructed away from the original fortifications forming today's Tretower Court.

Over time the lords of Tretower favoured the more luxurious Court and the castle fell into disuse.