The Castle takes its name from 'The Dean' or wooded valley - a common place name in Scotland. The original keep dates from around 1350 with the Palace being added around 110 years later. Built by the Boyd family, it has strong historical connections with many people and events in Scottish history - Robert the Bruce who gave the lands to the Boyds, James III whose sister married a Boyd, the Covenanters - some of whom were imprisoned there, Bonnie Prince Charlie - whose rebellion was joined by the 4th Earl of Kilmarnock and Robert Burns who was encouraged to publish his poems by the Earl of Glencairn who owned the castle at the time.
After a fire gutted the Castle in 1735, the Castle suffered two centuries of neglect before being restored by the 8th Lord Howard de Walden who inherited the Estate in 1899. His son, the 9th Lord gifted the castle to the town of Kilmarnock in 1975, including its magnificent collections, and in 1976 it was opened to the public. The collections of Arms & Armour, historical musical instruments and tapestries are some of the finest anywhere in Europe.