This report described radiographic and CT features of atypical diffuse idiopathic skeletal hyperostosis in a 5 year-old, female Shih-tzu showing marked proliferative bone lesions in the appendicular skeleton with minor spinal changes. Continuous or flowing bony bridge formation of vertebrae is used as the gold standard for diagnosing diffuse idiopathic skeletal hyperostosis. However, this criterion seems not to be suitable for appendicular type diffuse idiopathic skeletal hyperostosis, as in the present case. Diffuse idiopathic skeletal hyperostosis is a progressive skeletal disease, and thus, enthesophytosis and the multiple bony proliferations at insertion sites of ligaments and tendons to appendicular bones in a lamellar or trabecular pattern were considered diagnostic features of the appendicular type of diffuse idiopathic skeletal hyperostosis.