Dates are uncertain for the earliest parts of Sorn Castle, but the original tower seems to have been of late 14th century origin or earlier and the first known occupants were the Keiths of Galston. The castle occupies an admirable defensive position poised on a cliff above the River Ayr. Around the end of the 15th century, the tower was extended and the distinctive corbelled parapet was probably added at this time.
Additions on the landward side seem to have been made in 1793 - partly in the Adam style reminiscent of Culzean Castle. The Somervell Family remodelled the castle in the 1860s. William Railton of Kilmarnock submitted a design in 1862, but a scheme by the famous Edinburgh architect of the Baronial style, David Bryce, was implemented in 1864.
Bryce's entrance front was modified shortly after 1908 to the designs of HE Clifford for the new owner, Thomas W McIntyre. Clifford added a new billiards room wing on the left of the entrance and also remodelled the interiors. A turbine house was added near the castle and the dam was raised in order to produce electricity.
The castle is in private ownership and currently operates as a hotel.