The primary cardiac lymphoma is extremely rare. A case is presented of a 60 year old female patient with non-Hodgkin lymphoma of probable primary cardiac localization and with subsequent extension to peripheral lymph nodes. She had had a febrile syndrome for 8 months. Two two-dimensional echocardiograms gave negative results. Due to a syncope with atrial fibrillation, a transesophageal echocardiogram was carried out, which showed tumors in both atria, interatrial septum and right ventricle. The later appearance of right preauricular lymph nodes and left supraclavicular nodes led to a biopsy which confirmed a diagnosis of diffuse non-Hodgkin lymphoma with large immunoblastic cells. The patient died 15 months after the first symptoms, having undergone 6 chemotherapy cycles. The autopsy showed remission of the macroscopic lesions but presence of microscopic lesions in the cardiac chambers with histology and phenotypic markers identical to the ones found in the lymph nodes.