In this report, a 4-year-old male cat which was brought to Selcuk University, Faculty of Veterinary Medicine, Department of Internal Medicine clinics because of increased dyspnoea, anorexia, weight loss, nasal discharge and excessive salivation over a few days is described. In haemotochemical analysis, leukocytosis, hyperkalaemia, low venous partial pressure and saturation of oxygen level along with azotemia and hypocholesterolemia were determined. For further diagnosis, imaging techniques such as ultrasonography, radiography and computed tomography were performed. While no abnormalities were observed in abdominal ultrasonography, severe left mediastinal shift was detected on radiography; heterogeneous, hypodense areas interpreted as necrotic and granulomatous areas on computed tomography were observed. A diffuse granulomatous pneumonia with severe mediastinal shift was diagnosed based on clinical and laboratory analyses. Humane euthanasia was performed at the request of the owner as cat’s general condition started to worsen. The diagnosis was confirmed in the necropsy. In addition, fungal cell walls were observed around the necrotic areas and it was determined that the agent is Cryptococcus. As a result, the diagnostic differentiation and difficulties of dyspnoeic cats were stated through a case of a cat with respiratory distress due to diffuse granulomatous pneumonia accompanied by necrotic areas and Cryptococcus, and it was concluded that the management protocol which was performed in the present case would be beneficial for clinicians.