Craniomandibular osteopathy was diagnosed in two Pyrenean mountain dogs with a history of mandibular swelling, pain, fever and, in dog 1, lameness. Radiographs demonstrated extensive, active new bone formation on the ventral aspect of the mandibular bodies of both dogs. Dog 2 responded well to treatment but dog 1 was euthanased owing to severe pain, dysphagia and unsuccessful treatment. The mandibles were examined by means of back-scattered scanning electron microscopy and a well arranged mineralised trabecular network of chondroid tissue and woven bone was observed. The mandibular cortical bone under the areas of periosteal proliferation was also affected, showing a looseness of the characteristic compact appearance of lamellar bone. This is the first report of craniomandibular osteopathy in this breed.