ABSTRACT:An eight-year-old, 4.9 kg, intact male mongrel dog presented with progressive weight loss, anorexia, vomiting, diarrhoea, and open-mouth breathing. A thoracic radiograph showed significant pleural effusion. Upon removal of the pleural effusion, an oval-shaped soft-tissue density mass was identified above the heart base. Two months later, the dog's condition worsened severely, and he was euthanised. A complete necropsy showed all intrathoracic structures were encapsulated by a fibrinous material. A large granuloma was attached between the right cranial lung lobe and the trachea. The cytological evaluation of the pleural effusion showed numerous negative-staining rod structures. Ziehl-Neelsen staining confirmed the presence of acid-fast bacilli. A polymerase chain reaction test confirmed Mycobacterium tuberculosis infection. This work is the first case report of canine pulmonary M. tuberculosis infection in South Korea. To the best of our knowledge, the formation of giant tubercles in canine pulmonary tuberculosis has not been reported recently.Keywords: dog; M. Tuberculosis; pleural effusion; tubercles; tuberculosis List of abbreviations ALP = alkaline phosphatise, ALT = alanine aminotransferase, AST = aspartate transaminase, IL-6 = interleukin-6, PCR = polymerase chain reaction, TB = tuberculosis, TNCC = total nucleated cell count