Adam’s dining room spans the southern end of the ground storey of the principal block, between the sculpture gallery and the ante room and staircase. It is composed of a rectangular room with screened apsidal ends. Adam created the space by knocking together two older rooms on the south front. In 1807 a new dining room was built on the other side of the house, and at that time Adam’s dining room was transformed into a library by the addition of bookcases in the apses and on the window piers. In this altered state the room is reminiscent of the library at Kenwood.

Adam’s ceiling in the room was originally painted blue, buff and black. According to Eileen Harris, this was Adam’s earliest attempt at the Etruscan style, and Peter Leach has described it rather well as ‘tentatively Etruscan’. The Etruscan style was bolstered by the addition of Etruscan style furnishings designed in 1775-84. It has been suggested that the Etruscan furniture in Adam’s dining room at Newby was inspired by that which Adam had designed for Weddell’s brother-in-law, Sir John Ramsden, at Byram Hall, Ferrybridge, but observation of the drawings show that it was the other way around, and the designs for Newby predate those for Byram by around five years. Very little of the Etruscan scheme in Adam’s dining room survives as the furniture has largely been lost or moved, and the ceiling colour scheme has been lightened to blue, buff and red.

There is an Adam office grey-washed finished drawing duplicate of this design at the West Yorkshire Archive Service in Morley (WYL5013/D/1/7/1).