Malignant fibrous histiocytoma (MFH) is a pleomorphic sarcoma, occurring most frequently in the deep soft tissues of the extremities, and it is most frequently seen in elderly patients. A primary MFH of the diaphragm is very rare, and to the best of our knowledge, a multi-phased spiral CT appearance of this tumour has not been previously reported. In this report, we describe the clinical and multi-phase CT features of a primary MFH of the diaphragm.