Dystrophic calcinosis cutis associated with spontaneous hyperadrenocorticism was diagnosed in a 8-yearold female Chihuahua dog with erythematous, erosive, numerous papules, plaques, and crusts on the bilateral trunk, and inguinal region. Serum biochemical abnormalities included increases in alkaline phosphatase (ALP), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (GGT), and cholesterol. Radiographs showed mild hepatomegaly and subcutaneous lobulated calcific deposits. Histopathologic examination demonstrated diffuse deposition of basophilic calcified material in the dermis. Von Kossa's stain confirmed calcium deposition. Therapy with diltiazem was useful in resolving calcinosis.