The thymus is a primary lymphoid organ of the immune system, that plays a vital role in the development and maturation of the immune system during childhood. During the dissection we encountered an unusual thymus, located in the anterior mediastinum, which had a narrow, L-shaped accessory lobe and was located on the right side of the pericardium, covering the right ventricle from its base to the place of adhesion to the diaphragm. Its length was 6.7 cm, the width of the narrowest segment was 1.1 cm, and at the widest part was 2 cm, with the average segment thickness of 0.4 cm. The presence of accessory thymic lobes that extend till the level of the diaphragm creates difficulties during surgery especially in case of thoracoscopic procedures as the tissue lies on the pericardium in a narrow space thus making the dissection more difficult.