Ascending aortic false aneurysm is a rare but serious complication of pericardial mesothelioma. We report a case of ascending aortic pseudoaneurysm due to spindle cell pericardial mesothelioma. In this case, the first symptoms of the disease appeared 18 months before surgery. The final diagnosis was determined only when severe late complications occurred. Palliative tumour excision, aortoplasty and aortic valve prosthesis were performed with subsequent adjuvant chemotherapy. Over 10 months after surgery, the patient is alive and a significant reduction of the tumour mass has been achieved. This case demonstrates that timely lifetime diagnosis of malignant pericardial tumour remains very difficult and effective adjuvant chemotherapy is needed to improve the results of surgery.