The State Dining Room, at the time of its completion, was described as having the dimensions of a hall. Though redecorated a number of times, its basic features remain intact. The dignity of the room is created by its furniture, designed and built by James McEwan and Company. The centrepiece is the table of Spanish mahogany which seats 54 people.

The table is complemented by a substantial sideboard of mahogany and cedar set in an alcove; the sideboard is surrounded by elaborately carved woodwork and surmounted with a crown. On either side of the sideboard is a mantelpiece of black Belgian marble.

At each end of the room are portraits of members of the British Royal family; Queen Victoria; King George V and Queen Mary. The official portraits of King Edward VI and Queen Alexandra were presented to the house in 1902. There are also signed lithographs of King George VI and Queen Elizabeth, the Queen Mother. A number of portraits on loan from the National Gallery of Victoria also hang in this room.

As in the State Drawing Room and Ballroom, the ceiling consists of deeply recessed panels. The decorative scrollwork on cornices, cross beams and arch mouldings was once emphasised in a variety of colours, but today the tones are muted.

This room looks its best when arranged for a grand occasion, such as a State Dinner. A curiosity of this room is the 'door to nowhere', added by architects to retain symmetry.