The origin of the word Slebech is thought to be Viking meaning "stony beach". It is very probable that the Vikings sailed inland as far as Slebech and its commanding position over the waterway with the small harbour would be a natural place of refuge.
The oldest building still standing at Slebech Park today is the tower of the ruined church which is thought to date from the 12th Century. This was possibly a watch tower strategically positioned on the bend in the estuary as a forward garrison of the castles further inland at Picton and Llawhaden. It is similar to other structures of the same period that are to be found in Western Europe, notably in Portugal and was one of a number of fortified structures on the waterway or the coast of Pembrokeshire built by the Normans when they annexed the south of the county.
Slebech holds an important position in the history of Wales. During the 13th and 14th centuries it was home to the most powerful monastic foundation in Wales. It was a hospice of the Knights of St John and as such was a resting place for pilgrims en route to St Davids and a gathering point for the crusades. The only remaining structure associated with these times is the ruined 13th century Church in the grounds with the Norman watch tower as its bell tower.
After the reformation the Church became the Parish Church until 1848 when the roof was removed and it was replaced by a new Victorian Church which is also derelict today. The association with the Knights of St John has remained and today the original ruined church and its church yard still belongs to the order of St John (St John Ambulance).
As a result of the hospice, Slebech became an important crossing point of the waterway and unusually had lands both sides of the estuary. The Park was not created until 1760 when Slebech Hall was built on the site of the old commandery of St John.
Slebech Hall remains today very much as it was built in 1760 except that it's crenulations have been removed. It is one of the few Georgian Houses remaining in Wales today. The majority of the Coach House was built about the same time as Slebech Hall.