Lung lobe torsion (LLT) is an unusual life threatening disease in dogs. It can be defined as rotation of a lung lobe along its long axis with twisting of the bronchovascular pedicle at the hilus. It may be spontaneous, but is typically associated with predisposing conditions. Large deep-chested dogs appear to be more commonly affected. In dogs, the right middle lobe has been reported as the most commonly affected. Pleural effusion is a common clinical finding in dogs with LLT. It may be a cause or predisposing factor of LLT, depending on the case, and this is generally difficult to be established. A 35 kg, two-year-old male mix-breed dog was presented at Sena Madureira Veterinary Hospital with dyspnea, pale mucous membrane, very lean body condition. Severe hepatomegaly was noted during physical examination, besides hypophonesis on thoracic auscultation. Rectal temperature within normal limits. Owner reported prostration and avoidance to exercise the previous two weeks, with worsening of breathing pattern the last 2 days. Thoracocentesis and pleural effusion drainage were performed by colleague the day before (1,5 liter of serosanguineous fluid), with partial improvement of respiratory pattern. Radiographic examination showed pleural effusion, pneumothorax (not drainable), and pulmonary opacity/consolidation. Ultrasonographic examination of the thorax revealed a mass in left hemithorax. Due to animal's suffering, owner opted for euthanasia. At necropsy, moderated pleural effusion was seen; cardiomegaly, with severe dilation of right atrium and ventricle. Adherence and hepatization of left middle lung lobe. At dissection, torsion of bronchus and fibrosis of parenchyma of this lobe was noted. Severe hepatomegaly, occupying almost the entire abdominal cavity. Dilation of cava vein and hepatic vessels. At microscopic exam, the lobe with torsion showed fibrosis and necrosis areas. Areas of severe congestion and pneumonia were seen in other areas of the lung. Probably, the main disease was the lung lobe torsion, with secondary dilated cardiomyopathy and hepatomegaly.