This room dates from the 1760s redecoration of Castletown undertaken by Lady Louisa Conolly and reflects the mid-eighteenth century fashion for separate dining rooms. Originally, there were two smaller panelled rooms here. It was reconstructed to designs by Sir William Chambers, with a compartmentalised ceiling similar to one by Inigo Jones in the Queen's House at Greenwich. The chimney-piece and door cases are in the manner of Chambers. Of the four doors, two are false.

Furniture original to Castletown includes the two eighteenth-century giltwood side tables. Their frieze is decorated with berried laurel foliage similar to the door entablatures in the Red and Green Drawing Rooms. The three elaborate pier glasses are original to the Dining Room. The frames are carved fruiting vines, symbols of Bacchus and festivity. These are probably the work of the Dublin carver Richard Cranfield (1713-1809) who, with the firm of Thomas Jackson of Essex Bridge, Dublin, was paid large sums for carving and gilding throughout the house. The centre glass is cracked and it is said that at the end of a day's hunting, Tom Conolly brought home a stranger to supper who turned out to be the devil. A priest was called who threw a prayer book at the devil, this rebounded off the mirror and cracked it. The devil disappeared in a puff of smoke through the hearthstone which is also cracked. The twelve dining chairs, with carved vine leaves on the top rail, are copies of the Castletown originals and were made by the firm of James Hicks, the Dublin cabinetmakers.

The portrait, on the west wall, is of William Conolly in his robes as Speaker of the Irish House of Commons by Stephen Catterson Smith the elder (1806-1872) (donated by Mr and Mrs Galen Weston). This posthumous portrait was based on Jervas's portrait of the Speaker in the Green Drawing Room.

Opposite is a portrait of Speaker Boyle, later Ist Earl of Shannon, by Charles Jervas (c.1675-1739) standing full length in the Speaker's robes. The picture is inscribed and dated 1736 and has a very finely carved Irish eighteenth-century gilt frame (on loan from the Earl of Shannon).

Over the chimney-piece is a portrait of Owen Wynne of Hazelwood, County Sligo, attributed to John Michael Wright the younger (floruit circa 1690) standing in full length classical dress. This picture originally hung at Rockingham, County Roscommon (on loan from the Hon. Desmond Guinness).

On either side of the chimney-piece are portraits of Paul and Elizabeth Barry by George Mulvany R.H.A. (1809-1869) (donated by Mrs Annabelle Montague Smith in memory of her husband Patrick).

All text copyright of Dr. Paul Caffrey. Copies of the guidebook are available from Dr. Caffrey at caffreyp@ncad.ie