We report six patients with soft tissue sarcoma mimicking traumatic hematoma. The lesions in these patients, showed huge hematomas and were characterized by rapid growth. Cytology of percutaneous; aspiration biopsy samples was performed in all six patients; however, in five patients, findings for malignant cells were negative. Consequently, they were misdiagnosed, resulting in a poor prognosis. We conducted a retrospective study in which we evaluated the clinical findings, the magnetic resonance (MR) images, and computed tomography (CT) scans of the soft tissue sarcomas forming huge hematomas in the lesion. MR imaging revealed the fine tumor mass with enhancement and characterized the hematoma in the lesion in a more precise fashion than did CT. We conclude that MR imaging is a suitable method for differentiating these soft tissue sarcomas from chronic traumatic hematoma.