The association between dermatomyositis and restrictive cardiomyopathy has not been reported before. We present here the clinical, echocardiographic and muscle biopsy data for a patient with dermatomyositis and restrictive cardiomyopathy. In a 78-year-old male with a history of arterial hypertension, recurrent episodes of atrial fibrillation and syncopes, rupture of an infra-renal aortic aneurysm with complications (recurrent QT-prolongation, lumbo-sacral plexopathy, transient ischaemic attack, peripheral embolism), monoclonal gammopathy, subdural haematoma, focal seizures, megaloblastic anaemia, leucopenia, eosinophilia, elevated muscle enzymes and increasing tiredness, dermatomyositis was diagnosed upon clinical presentation, muscle enzyme and muscle biopsy findings. Cardiological examination revealed atrial fibrillation, left anterior hemiblock and restrictive cardiomyopathy. After the exclusion of various differentials for restrictive cardiomyopathy, a causative relationship between restrictive cardiomyopathy and dermatomyositis was assumed. This case suggests the need for suspecting restrictive cardiomyopathy in patients with dermatomyositis. Patients with dermatomyositis should undergo a comprehensive cardiological investigation as soon as the neurological diagnosis is established.