An unusual presentation of blunt chest trauma is reported. A 21-year-old man presented with symptoms and signs of congestive cardiac failure. 2D echocardiogram showed a thickened pericardium with a mass compressing the right ventricle. CT scan revealed a large mass anterior and to the right of the heart with evidence of pericardial thickening and calcification. However, its delineation from the pericardium and its exact tissue characterization were not possible. Cardiac catheterization showed elevation and equalization of diastolic pressures in all cardiac chambers with characteristic waveforms suggestive of pericardial constriction. The precise definition and characterization of the mass was obtained only on Magnetic Resonance Imaging (MRI) of the chest which showed it to be a solid, well encapsulated, partially calcified mass between the heart and the diaphragm extending anteriorly and to the right of the right ventricle. These findings were confirmed at the time of thoracotomy. Histopathology revealed blood clots and hyalinised fibrous tissue without any evidence of granuloma or malignancy. This report highlights an insiduous, late presentation of blunt chest trauma. It also demonstrates the superiority of MRI over computed X-ray tomography for mediastinal paracardiac masses.