[3] Known as Kilmarnock Castle until 1700, it gradually took its name from the dean or wooded valley, a common place name in Scotland.

Owned originally by the Boyd family, it has strong historical connections with many people and events famous in Scottish history.

Robert the Bruce who gave the Boyds these lands; James III of Scotland whose sister married a Boyd; the Covenanters, some of whom were imprisoned here; Bonnie Prince Charlie, whose rebellion was joined by the 4th Earl of Kilmarnock and Robert Burns who was encouraged to publish his poetry by the Earl of Glencairn who owned the Castle at that time.

Dean Castle and Country Park is maintained by East Ayrshire Council and is free to access.

The banqueting hall displays many items owned by East Ayrshire council including Kilmarnock Edition of Robert Burns poetry and many works of art.

Legend has it that after the 4th Earl of Kilmarnock was beheaded for treason in London on 18 August 1746 his head was carried back to Dean castle and was stored in a large chest which is still present in the Laigh Tower.

The Robert Burns World Federation recently unveiled a plaque to the memory of those who lost their lives in the terrorist attacks on 11 September 2001.

Illumnight, a light show, was created in 2017 and by its second year had attracted over 80,000 visitors and had become one of the UK's most speculator illumination event.

It was built mainly for defence, the walls are 2–3 metres thick, it has few windows, and the original entrance is high above ground level.

In its current form, the keep houses many artefacts belonging to the Boyd family and medieval times in general, as well as various collections of arms and armour.

However, it is carefully copied from real sixteenth-century buildings, including details like the windows with half-wooden shutters and half-leaded glass.

The Hall also served as a court as the lord would act as a judge passing verdicts and sentences for crimes committed in the surrounding area.

This room would also have been used by the minstrels to sleep in; the reason for them having their own private quarters was that it was feared that many of them would have been carrying disease.

The guard room has the only access to the dungeon in the castle, a small hole in the floor where prisoners were thrown in.