The first Agricultural Show in the Demesne was held on 22nd August 1928.
The show secretaries were Mr J.G. Jamison, Miss Ryan and Mrs P.D.Savage.

There were classes for horses, cattle, swine, sheep, goats, poultry, butter and eggs, grazing fields, baking, embroidery and crochet, art, handicrafts, children's flowers, horse jumping and sheep dog trials. 1939 was the last show.

In 1967 a new seven man committee in partnership with the Ulster Riding and Jumping Club organised the first Horse Show in Castlewellan since 1939. The date was that used by URJC ie. the first Saturday after the 12th July holidays
This partnership continued until 1982 when the two committees agreed to go their separate ways, and the show was organised solely by the Castlewellan show committee.

1983 saw the inclusion of the local riding club show run by Newcastle & District Riding Association. The cattle and sheep sections have continued to grow and every year new classes are introduced, while show day would not be the same without the colourful trade stands, bouncy castle and fun fair.

Years on from that first revival Castlewellan Agricultural Show is still going strong with over 300 classes, and is recognised as one of the foremost one-day shows in the country and is still a good day out for the family.