Welsh Newton village is in the south-west of the county, less than one mile from the Welsh border. The castle lies approximately one mile to the north-west of the village.
The castle occupies a roughly rectangular site, 36m by 27m, and is surrounded by a moat and a curtain wall with a thickness of 1.4m. The castle lies on a slope, and the ditch is kept wet by a substantial outer bank. The structure consists of ashlar, local sandstone and rubble walls.
The earliest part of the castle is the four-storey round tower or keep at the west angle, which is thought to date from the late 12th century or early 13th century. The tower has an internal diameter of only 7.5m but is still thought to have been the keep of the castle. The internal rooms of the tower are only 5m wide and there was no stair within the walls. A semi-circular projection on the south-east may be the remains of an external stairway. The upper two floors would have been accessed via internal wooden stairs.
Externally, the keep tower is divided into two stages distinguished by a moulded string-course. This tower contains several original arrow-loops, and on the third storey there is a corbelled latrine projecting out onto the south-east side. The top floor of this tower contains what may be the original fireplace.
The hall block and other domestic buildings adjoining the tower may be of the same 12th/13th century date. In the 17th century the hall block was replaced by the still inhabited house. The hall is of two storeys with rubble walls and a modern crenellated parapet.
In the north corner of the court is a 16th century chapel with 17th century windows. Underneath the chapel is a 13th century vaulted undercroft. The chapel contains an altar and gallery, as well as a piscina and screen.
The gatehouse and the curtain walls were built in the second half of the 13th century, and the crypt of the chapel is probably of the same date. The gatehouse passage was once defended by a portcullis and wooden doors and was flanked by round towers 6.5m in diameter. The fireplace in the upper area of the gatehouse is of c. 1500 and coincides with alterations of this date.
This castle was originally called Newland Castle and was most probably built by Matilda de Valery (later de Braose) sometime before 1208.
1208: The castle passed to the Pembridge family. This is probably the date of its renaming as Pembridge Castle.
1265: In this year the Pembridge family lost their land at Pembridge to Roger Mortimer of Wigmore, Pembridge Castle now became their principal seat. Richard de Pembridge, who was a Knight of the Garter and Warden of the Cinque Ports, once occupied Pembridge Castle.
1387: The castle subsequently passed to Sir Richard Burley, who died in possession of it in this year; the castle then passed to Edmund Tudor, half-brother of Henry VI.
1445: The castle passed into the Hopton family who later sold it to Sir Walter Pye.
1640s: During the Civil War the castle served as an outpost to royalist Monmouth.
1644: The castle was captured in this year by Colonel Scudamore and garrisoned by the Parliamentarians until 1646, when it was ordered to be slighted.
Post-1646: The castle was sold to George Kemble, who endeavoured to make it habitable again. St. John Kemble, who was executed in Hereford for his faith in 1679, had his oratory there.
1715: Pembridge Castle was occupied by Henry Scudamore. It later passed to the Townleys of Lancashire, and was later sold to the Baileys, but the occupants at this period were tenant farmers.
20th century: The castle was heavily restored during this period, the gatehouse was repaired and the south gatehouse tower rebuilt. The curtain walls were rebuilt and new crenellations added.