It was built mainly in Gothic style, but has Renaissance architectural elements. It features tall and strong defence towers, an interior yard and a drawbridge. Built over the site of an older fortification and on a rock above the small river Zlaşti, the castle is a large and imposing building with tall and diversely colored roofs, towers and myriad windows and balconies adorned with stone carvings.
The first step was building a double wall for fortification purposes. The walls were flanked by rectangular or circular towers, an architectural innovation to the period's Transylvanian architecture. Some of the towers (the Capistrano Tower, the Deserted Tower and the Drummers' Tower)were used as a prison. The Buzdugan Tower (name after a type of weapon)was solely built for defence purposes and it had its exterior decorated with geometric motifs. The rectangular shaped towers had large openings to accommodate larger weapons. The castle has 3 large areas: the Knight's Hall, the Diet Hall and the circular stairway. The halls are rectangular in shape and are decorated with marble. The Diet Hall was used for ceremonies or formal receptions whilst the Knight's Hall was used for feasts. In 1456, Iancu de Hunedoara died and work on the castle has stagnated. Starting with 1458, new commissions were being undergone to construct the Matia Wing of the castle. In 1480, work has completely stopped on the castle and it was recognised as being one of the biggest and most impressive buildings in Western Europe.
The XVI century did not bring any improvements to the castle, but during the XVII century new additions have been made, for aesthetic and military purposes. Aesthetically, the new Large Palace has been built facing the town. A two level building, it hosted living chamber and a large living area. For military purposes, two new towers were constructed: the White Tower and the Artillery Tower. Also, the external yard was added, used for administration and storage.
The current castle is the result of a fanciful restoration campaign undertaken after a disastrous fire and many decades of total neglect. It has been noted that modern "architects projected to it their own wistful interpretations of how a great Gothic castle should look".