Carew Castle stands on the banks of the River Carew, a short distance before the river opens out into the Milford Haven estuary. Gerald of Windsor constructed an early motte and bailey castle here around 1100AD on the site of an earlier Iron Age fortification. It consisted of an outer wooden wall and stone keep. Gerald obtained the land as a dowry, through marriage to Nest, princess of Deheubarth.

Nest is famous in her own right as "The Welsh Helen of Troy" and "the most beautiful woman in Wales". She was later abducted from another castle, probably Cilgerran, by Owain ap Cadwgan. Legend has it that she persuaded Gerald to flee down a latrine to avoid capture. She was held by Owain for six years before her re-capture, and bore him two children.

Gerald's son William was the first to use the name "de Carew". In the middle of the 12th century, he built a great hall and enclosed it, along with the keep, inside a stone wall.

Around 1270AD, Nicholas de Carew erected a series of rooms and halls around the inner circumference of the curtain wall. This is the high-walled structure, along with its three towers, that can still be seen today.

Carew Castle fell into the hands of Rhys ap Thomas after the de Carew family were forced to mortgage it following the black death. When his grandson was executed for treason by Queen Mary in 1558AD, the castle was granted to Sir John Perrot, who converted it into a luxurious Tudor mansion. Perrot eventually fell out of favour with the crown and was imprisoned in the Tower of London. Eventually, the castle was re-purchased by the de Carew family in 1607AD.

During the English Civil War (1642–1651AD), Carew Castle was fortified and used as a Royalist base. It changed hands multiple times, before Royalists eventually demolished the south wall to render the castle defensively worthless. Following the Restoration, the de Carews returned and occupied the east wing. In 1686AD, the castle was abandoned and fell into decay.

Today, Carew Castle stands as an imposing ruin, offering a romantic and evocative image to visiting tourists. It is still owned by the descendants of the de Carews, and is leased to Pembrokeshire Coast National Park. The shell of the castle is mostly in tact, and the great hall has been re-roofed. There is much here to see, and I would highly recommend making some time to stop by if you find yourself in Pembrokeshire.