Earthworks were dug on the site in the early 12th century and these were besieged by William the Lion, King of Scotland in 1173 and 1174. These sieges were unsuccessful but the threat of further attacks by the Scots caused Henry II to agree to a allow a stone castle to be built on the site.
The attractive square keep of Prudhoe Castle was constructed in around 1175 and was surrounded by curtain walls and a gatehouse. The keep was one of the first to be built in Northumberland.
In the 13th century a moat was dug and the castle was also provided with two barbicans and a stronger gatehouse. The gatehouse had a vaulted basement and a chapel on the first floor.
The chapel had a oriel window which is considered to be one of the earliest to be found in any English castle.
Prudhoe castle passed into the hands of the Percy family in 1381.