Atypical lipomatous tumors, so-called well differentiated liposarcomas are the intermediate or locally aggressive form of adipocytic tumors. Mediastinum is an uncommon localization for these tumors and they have a potential risk of recurrence following excision. We herein report a case with a giant atypical lipomatous tumor located at the mediastinum that was surgically excised. The patient is free of recurrence and asymptomatic at postoperative 17 months. Surgery remains as the treatment of choice for mediastinal liposarcomas.