It belongs to Dinaric Alps, and it stretches from the pass of Klis in the southeast, to the above Split Airport in the northwest. The highest peak is Veli vrj (779 m) above Kaštel Gomilica. Its southern slope is very steep, and northern rock slopes gradually turns to the corrugate plateau of Dalmatian Zagora. Kozjak is mainly composed of karst — limestone rocks.
Mali Kozjak in town of Kaštela is more known then Veliki Kozjak above the village of Kijevo. On the west side of the ridge is well-known mountain centre of Malačka on 477 m.