Manorbier Castle began life in the late part of the 11th Century as a wooden motte-and-bailey fortification, built on land granted to Odo de Barri following the Norman conquest. Odo's son, William de Barri, began work to rebuild the castle in stone in the early part of the 12th Century.

Manorbier Castle enjoyed a relatively peaceful history, experiencing only two minor assaults - once in 1327AD as a result of a conflict over the family succession, and then again in 1645AD during the English civil war. At this time, the Parliamentarian forces "slighted" the castle to prevent its further use as a fortification. It was considered derelict in 1670AD when it was sold to the Philipps family. Subsequently, it fell into decay until it was partially restored in 1880AD by the tenant at that time, J.R.Cobb. Today, the castle is still in private hands, and is owned by Lady Dunsany (who is descend from the Philipps family).

Manorbier Castle is known for being the birthplace of the famous scholar Gerald of Wales, in 1146AD. Gerald was descended on his mother's side from the equally famous Nest verch Rhys (the "Helen of Wales"), whose abduction by Owain ap Cadwgan is famously documented in the "Chronicle of the Princes". Gerald is remembered for his vivid and detailed written accounts of life in medieval Wales, such as his "Journey through Wales" - an account of his tour of the country with Archbishop Baldwin in 1188AD.

Today, Manorbier Castle is tastefully preserved and maintained by its private owners, enjoying a picturesque location well removed from the beaten track - a location described by Gerald as "the pleasantest spot in Wales". Private ownership of the castle has allowed it to retain its own unique character, distinguishing it from the slightly sanitised feel normally associated with properties in the hands of the established heritage organisations.