A 12-year-old Welsh pony mare was presented to the Ontario Veterinary College Teaching Hospital for signs of intermittent lethargy and increased abdominal breathing effort of 6 months duration. After physical examination, blood work, bronchoscopy, bronchoalveolar lavage, and diagnostic imaging of the thorax and attempted lung biopsy, pulmonary mineralization of unknown origin was suspected. The pony was treated palliative for 7 months with nonsteroidal anti-inflammatories and inhaled corticosteroids to treat accompanying airway inflammation before being euthanized because of poor prognosis and deterioration of clinical signs. On postmortem examination, the pulmonary architecture of the right and left cranioventral lung lobes, accessory lobe, and cranial potions of the left caudal lung lobe was replaced by hard mineralized tissue. No other organs other than a mediastinal lymph node and the lung were affected by mineralization. After decalcification, thick sheets of fibrous connective tissue organized into layers and lamellae replaced the normal architecture of the pulmonary parenchyma in more than 90% of the lung lobe examined on histopathology. The findings were consistent with generalized severe pulmonary fibrosis and dystrophic calcification.