The first motte-and-bailey castle (ca.1093) was built a mile away from the present site,[4] probably about the time of the founding of the town by Roger de Montgomery, a Norman baron.

The same year, Owain Gwynedd led the defeat of the Norman rulers in the town of Cardigan at the Battle of Crug Mawr.

[citation needed] Llywelyn the Great captured it in 1215[4] and at the parliament held at Aberdyfi in 1216 made it over to the sons of Gruffydd ap Rhys of Deheubarth, but in 1223 William Marshall the Younger recaptured it.

On Llywelyn's death it fell back into Norman hands, and in 1244 Earl Gilbert of Pembroke rebuilt it with town walls for added protection.

[8] The castle was purchased by Ceredigion County Council in April 2003 and repairs began as part of the regeneration of Cardigan.

In 2004 Castle Green House appeared on the BBC's second series of Restoration, presented by Griff Rhys Jones.

[9]: 148–155 Renovation work continued for some years after its purchase by the Council,[10] and the castle was opened to the public on 15 April 2015[11] with a concert held in July 2015.