Abstract Background Primary cardiac lymphomas (PCL) represent extremely rare cardiac tumors which are accompanied by poor prognosis, unless they are timely diagnosed and treated. Case presentation Herein we present a 28-year-old, immunocompetent man who presented to our hospital due to progressively worsening symptoms and signs of superior vena cava syndrome. Multi-modality imaging demonstrated a large intracardiac tumor, which was proven, by biopsy, to be a PCL. The patient received targeted chemotherapy which led to total remission of his disease, with no relapse over a 15-month follow-up period. Conclusions Although PCLs are rare, they should always be kept in mind in the differential diagnosis of cardiac tumors. Timely diagnosis of PCLs and appropriate chemotherapy, alone or in combination with radiotherapy, seems to provide the best results.