Nocardiosis is a suppurative to granulomatous, localized or disseminated bacterial infection caused by aerobic actinomycetes that are members of the family Nocardiaceae. Pulmonary nocardiosis is an infrequent but severe infection, which can behave either as opportunistic or primary pathogens. The present study report a case of pulmonary nocardiosis presented to the Veterinary Hospital at the University of Londrina (HV-UEL) in August 2008. A 9-month-old female mongrel dog was evaluated at the HV-UEL because of a weight loss, anorexia e dyspnoea with 21days duration. At the clinical examination the dog has presented fever, mild dehydration, purulent oculonasal discharge, dyspnea and decreased lung sounds. In complete blood cell count have anemia and neutrophilic leukocytosis with a left shift. The radiography revealed pleural effusion, bronchial and interstitial pattern. It has performed thoracentesis and 360ml of reddish fluid was removed. Cytologic analysis of the fluid sample revealed a red, opaque fluid that contained 3.8 g/dl of protein and 390,000 cells/mm³ (89% neutrophils, 7% macrophages and 4% lymphocytes). In the culture environment (using a fluid sample) has grown Nocardia species. The support treatment was fluid and oxygen therapy, and antibiotic therapy with enrofloxacin and ceftriaxone. The patient has died three days after beginning treatment. Pathologic findings were diffuses abscess formation in lungs. Pulmonary nocardiosis probably results from inhalation of soil organisms. Nocardial lesions develop in alveolar spaces and frequently erode into blood vessels, resulting in systemic spread of the disease. Predisposing factors increase susceptibility to nocardiosis, how infectious diseases, metabolic disorders, immunosuppressive drug therapy, or neoplasia. Usually the treatment involves prolonged use of antimicrobials. The mortality rate is high, because of delayed diagnosis, predisposing conditions, and inappropriate therapy, as seen in this case report that the animal has died before culture result. The antibiotics used wasn't primary drugs for treating nocardiosis, however, in vitro they have presented susceptibility.