Postpneumonectomy syndrome is a rare complication of pneumonectomy that develops as a result of excessive displacement of mediastinal structures into the empty cavity. We report the case of a 72-year-old man who developed dysphagia and progressive weakness, along with signs of hypotension due to low cardiac output, following removal of the left lung for lung cancer. Intubation and transfer to the intensive care unit was necessary. When such causes as pulmonary embolism, pneumonia and COPD exacerbation had been ruled out, postpneumonectomy syndrome was diagnosed. Two tissue expansion prostheses (100 mL and 400 mL) were implanted surgically to keep the mediastinum in position and reverse symptoms immediately. We conclude that postpneumonectomy syndrome after left pneumonectomy is a rare complication that may be more frequent than the literature suggests, given that signs may be masked by a diagnosis of cardiogenic shock that leads to death. Surgical repair is simple, reversing symptoms immediately.