The Fitzalans held the castle until 1556, when Mary married Thomas Howard (4th Duke of Norfolk) uniting the Fitzalans and the Howards and bringing Arundel to the Dukes of Norfolk who have held it ever since. In the 1640's, Arundel suffered its third, last and worst siege. The Castle fell into Parliamentarian hands during the Civil War, but on the December 9, 1643 surrendered to the Royalists. On December 19 the Roundheads began their siege, placing artillery in the tower of St. Nicholas Church that wrought such damage that the Royalist garrison surrendered. Cannon ball damage can still be seen on the walls of the Barbican Towers.

The Castle remained a ruin for nearly 150 years until the 8th Duke began restoration in 1716 with work continued by the 10th Duke in 1789, who rebuilt in the fashionable Gothic style. In the late 19th century, the 15th Duke swept away most of the architectural fantasy, and undertook a more straightforward reconstruction of the early Norman stronghold. The Castle with its circular Keep, double Bailey and a stone stairway up the mound to the Keep is essentially a smaller version of Windsor Castle.