Myxofibrosarcoma is a soft tissue neoplasm composed of malignant fibroblasts with a myxoid matrix. It is commonly found in patients during their 6th through 8th decades of life with a slight male predominance. Myxofibrosarcomas are classified as low- to high-grade tumors that are differentiated by hypercellularity, variation of mitotic activity and degree of necrosis. The most common sites are the extremities (77%) and trunk (12%), with the retroperitoneum and mediastinum being very rare. In this case report, we describe a patient presenting with myxofibrosarcoma of the mediastinum, a rare site for the development of myxofibrosarcoma. This case of primary mediastinal myxofibrosarcoma appears to be only the second described in the English-language literature.