The architecture is French-inspired, but the decoration is German in inspiration, and sources for the statues have been found in the work of the German engraver Hans Burgkmair. The statues include a line of soldiers on the south parapet, and a series of full-size figures around the principal floor. These principal figures include a portrait of James V, the Devil, St Michael, and representations of Venus and several planetary deities. Their arrangement on the north, east and south faces of the Palace has been interpreted in relation to the quarters of the heavens. The 19th-century architectural historian R. W. Billings described the statues as "the fruits of an imagination luxuriant but revolting". The west façade is undecorated and incomplete, and the Privy Council of Scotland noted in 1625 that the building was "schote over the craig."
Internally, the Palace comprises two apartments, one each for the king and queen. Each has a hall, presence chamber, and bedchamber, with various small rooms known as closets. The Renaissance decoration continued inside, although little has survived the building's military use, excepting the carved stone fireplaces. The ceiling of the King's Presence Chamber was originally decorated with a series of carved oak portrait roundels known as the Stirling Heads, described as "among the finest examples of Scottish Renaissance wood-carving now extant." The carvings were taken down following a ceiling collapse in 1777, and of an estimated 56 original heads, 38 survive. Most were given to the Smith Institute in Stirling, and these are now preserved in the castle, and three more are in the National Museum of Scotland, Edinburgh.
To the left of the gatehouse, and forming the south side of the Inner Close, is the Royal Palace. The first Renaissance palace in the British Isles, this was the work of King James V.
With its combination of Renaissance architecture, and exuberant late-gothic detail, it is one of the most architecturally impressive buildings in Scotland, covered with unique carved stonework. It was begun in the 1530s, and was largely complete by the time of James' death in December 1542.
The Master of Works, until his execution in 1540, was Sir James Hamilton of Finnart, who also financed part of the work, in return for land and favours from the king.
Further work was carried out during the regency of Mary of Guise, and the upper floor was converted to provide an apartment for the castle governor in the 18th century.