Sclerosing epithelioid fibrosarcoma (SEF) is a rare deep-seated tumor, that typically develops in the lower extremity, limb girdle, and trunk. This tumor is clinically aggressive, with a poor prognosis. The authors present an extremely rare case of SEF developing in the pelvis. The patient was a 75-year-old woman presenting with a solid mass located adjacent to the uterus in the left adnexal region on vaginal ultrasonography. MRI showed a lobulated solid mass exhibiting hypointensity on T1- and T2-weighted imaging. The tumor also showed heterogeneous signal intensity on diffusion-weighted imaging, and heterogeneous enhancement on dynamic study, and both features were distinct in the tumor’s peripheral zone. These MRI features were correlated with more hypercellularity in the peripheral zone on histology. To date, few reports have focused on the MRI features of SEF. Diffusion-weighted and contrast-enhanced MRI may provide more useful information for the diagnosis of SEF located in uncommon sites.