It was built in response to the First Welsh War in the late 13th century, replacing an earlier fortress located a mile to the south.

Marcher lord Gilbert de Clare built an earlier motte and bailey castle a mile south of the current site in around 1110.

[12] However, by the time of the Black Prince in 1343, the castle was in a bad state of disrepair; the main gateway and drawbridges, the king's hall and long chamber, the kitchen range, and the outer bailey were falling down.

[16] In 1637 Thomas Bushell prevailed upon Charles I to establish a Royal mint in Aberystwyth, sited in the castle hall.

[17] This was authorised to mint the half-crown, shilling, half-shilling, two-pence, penny, groat, threepence, and half-penny coins, from silver that was mined locally in Ceredigion.

[10] The inner ward was built in a diamond-shaped concentric castle,[20] with a twin D-shaped gatehouse keep and mural towers at each corner.