Architectural remains in Morava school style mean that Koznik was most probably built during prince Lazar Hrebeljanovic’s rule (1371-1389).
The fortress with seven towers was built on top of a steep hill dominating the surrounding terrain on 920 m altitudes. It was mentioned for the first time in a Prince Lazar Decree. In the early 15th century, Koznik belonged to Grand Čelnik Radič, one of the most important knights at that time.
Lazar's widow, Princess Milica, spent some time there in 1402, while their son, despot Stefan Lazarević, made two decrees in Koznik in 1405, granting Radič Postupović all surrounding villages and the church on the river Grabovničica.
After a brief Ottoman conquest of Koznik, in 1444 the castle was returned to despot Đurađ Branković. The Ottomans re-seized the castle in 1454-1455, when they conquered Kruševac.
During 16th and 17th century, an Ottoman squad was located there until 1689, when Koznik was taken hold of by Serbian rebels, which indicates that, at the time, Koznik was still an active fortification.
Koznik is an example of a small highland fortified castle. It has an irregular polygonal base that follows the configuration of the terrain. South from the fort were other constructions, with some remnants still recognizable today.