Calvarial hyperostosis syndrome (CHS), which has been recently defined in juvenile dogs, is a rare, non-neoplastic, proliferative bone disease characterized by the swelling of the skull. Until recently, it was mostly reported in young Bullmastiffs with a sexual preference for male dogs. The objective of this study was to describe the clinical and pathological aspects of the condition as a contribution to literature due to its rarity in dogs. The paper presents the first reported case of Calvarial hyperostosis in turkey. A four-month-old female American Pit bull terrier was presented to the veterinary physician with the complaints of painful swelling on the head, loss of appetite, lethargy and fever. Radiograph of the skull revealed diffuse thickening of the frontal and parietal bones and markedly increased bone opacity, and magnetic resonance imaging (MRI) scans revealed increased diploe thickness in all sequences. The preliminary clinical diagnosis of calvarial hyperostosis was confirmed by histopathology which revealed the presence of both immature woven bone and mature bone trabeculae separated by prominent basophilic cementing lines. The lesion is self-limiting, and most cases show spontaneous regression in few months, but in this case the patient was monitored until one year of age and no regression was seen.