The castle is roughly rectangular in shape with four circular towers at the corners. Unlike many castles Donnington did not have a separate keep, instead the strongest part of the castle was the large gatehouse which is now all that remains. The gatehouse is rectangular in shape projecting quite a distance beyond the main rectangular part of the castle and has two very tall drum-towers in front of it. The towers have several string courses running horizontally around them dividing the towers into several sections. A range of buildings would have occupied the central courtyard.
Richard Abberbury did not have any children and when he became old he sold the castle to Thomas Chaucer, the son of the poet Geoffrey. Thomas bought the castle in 1415 for his daughter Alice possibly as a wedding gift for her and her new husband Sir John Philip.
in 1643, during the English Civil War, the castle was captured and held for the King by Sir John Boys who built extra defences around it in line with the current military ideas of the time. The castle came under attack in 1644 and much of the castle was destroyed by the large number of missiles fired at it, but the other defences built by Boys held and the castle did not fall. The siege was lifted when Charles I arrived in Donnington with an army. The King rewarded Boys with a knighthood for his valiant efforts protecting the castle. But the victory was short-lived. The Royalist army retreated after the Second Battle of Newbury in October 1644 leaving thier guns at Donnington Castle under the command of Sire John Boys. Again the castle came under attack ang again Boys defended it against all that was thrown at it. After a siege of two years Sir John was allowed to surrender with full honours and a led his army out with their guns.