Cardiac herniation after pneumonectomy is recognized as a rare complication. This case report describes two cases. The mortality rate of this complication remains high as reported in the literature; in early-recognized cases 50 % and in late or unrecognized cases 100 %. In the following two cases a pneumonectomy was performed as a treatment for lung cancer. Within 48 h after the initial operative treatment, the clinical situation of the patients got worse and radiographic examinations showed a strongly deviated heart. After suspicion of the diagnosis, the patients were immediately transferred to the operation theatre for emergency thoracotomy. Per-operative the diagnosis was confirmed and the heart was returned into its original position while the defect in the pericardial sac was closed with a bovine pericardial patch. Both patients survived these procedures and did not suffer from any further complication.