Although originally a Norman stronghold the castle maintains a mixture of architectural styles as modifications were made to the structure over successive centuries.

The castle stands on a limestone bluff overlooking the Carew inlet, part of the tidal estuary that makes up the Milford Haven Waterway.

The site must have been recognised as strategically useful from the earliest times, and recent excavations in the outer ward have discovered multiple defensive walls of an Iron Age fort.

Nest brought the manor of Carew as part of her dowry, and Gerald cleared the existing fort to build his own castle on Norman lines.

Gerald's son William took the name "de Carew", and in the middle of the 12th century created an enclosure with stone walls incorporating the original keep, and a "Great Hall" inside it.

The current high-walled structure with a complex of rooms and halls around the circumference was created in about 1270 by Nicholas de Carew (d.1297),[4] concurrent with (and influenced by) the construction of the Edwardian castles in North Wales.

It fell into the hands of Rhys ap Thomas, who made his fortune by strategically changing sides and backing Henry VII just before the battle of Bosworth.

[5] Rewarded with lands and a knighthood, he extended the castle with luxurious apartments with many Tudor features in the late 15th century.

In 1558 it was acquired by Sir John Perrot, a Lord Deputy of Ireland, who completed the final substantial modifications of the castle.