St Brides Castle is located on the south side of St Brides Bay, to the north-west of Milford Haven. It is registered for the remains of enclosed garden and water features associated with the possible sixteenth-century mansion which are situated to the north-east of the new mansion. Parkland, terraces, walled gardens and formal gardens surround the Castle that was built on the site of `The Hill'.

St Brides mansion (erroneously called ‘The Abbey’), the original sixteenth-century house, was superseded by ‘The Hill’, built on a more elevated position to the south-west and this, in turn, made way for The Castle. Around ‘The Abbey’ there is group value with the Grade II* Listed ruins (LB 87482) and nearby Grade II Listed Church of St Bridget with its former rectory (LBs 18234 & 19399). Around the Grade II* Listed new mansion (The Castle, LB 13018) there is group value with Grade II Listed features of the adjacent stable yard (LBs 13016-7). The site also lies within the Pembrokeshire Coast National Park.

Today, the remains of the old mansion are usually reached from the drive to the Castle. They include two rectangular courtyards, now mostly surrounded by woodland. The smaller is on the east, the larger on the west. The smaller was once a rose garden but is now covered by roughly mown grass. Through the central arch in the western, castellated, wall is the larger courtyard. Within it has two changes of level and is now laid out to grass, trees and shrubs. The courtyards may have been laid out to (walled) gardens continuously from the fifteenth century until the early twentieth century. Two ponds were situated centrally within St Brides Green.     

The park dates from the eighteenth century and expanded in the nineteenth century to give the present-day open sweep of parkland. It is located a short distance from St Brides Haven, occupying the north-easterly sloping land to the east and north of the castle. It is separated from the headland and coastal path by a substantial dry-stone wall, originally up to 1.5m-2m high. Deer were once kept on the estate.

The main drive aproaches from the east through the Abbey woods. The area around The Hill and the Castle has probably always been put down to gardens. North of the Castle is woodland with ornamental plantings, accessed from the north-west of the house by recently uncovered steps. Along the south and east sides of the house are wide, buttressed, terraces of varying width, with steps down to informal lawns.