The castle was first built by a Norman baron in c. 1100 on a cliff above the River Nidd. There is documentary evidence dating from 1130 referring to works carried out at the castle by Henry I. In the 1170s Hugh de Moreville and his followers took refuge there after assassinating Thomas Becket.
In 1205 King John took control of Knareborough Castle. He regarded Knaresborough as an important northern fortress and spent £1,290 on improvements to the castle. The castle was later rebuilt at a cost of £2,174 between 1307 and 1312 by Edward I and later completed by Edward II, including the great keep. Edward II gave the castle to Piers Gaveston and stayed there himself when the unpopular nobleman was besieged at Scarborough Castle.
Philippa of Hainault took possession of the castle in 1331, at which point it became a royal residence. The queen often spent summers there with her family. Her son, John of Gaunt acquired the castle in 1372, adding it to the vast holdings of the Duchy of Lancaster. Katherine Swynford, Gaunt’s third wife, obtained the castle upon his death.
A detailed survey of the state of the castle buildings was made in 1561. The building was used by estate auditors and law courts were held in the hall.
The castle was taken by Parliamentarian troops in 1644 during the Civil War and largely destroyed in 1648, not as the result of warfare but because of an order from Parliament to dismantle all Royalist castles. Indeed many town-centre buildings are built of ‘castle stone’.