A case of Sertoli-stromal cell tumor of the right ovary is reported. The patient was a 50-year-old perimenopausal woman with abdominal distention due to a large pelvic tumor. She had no signs of androgen excess. A large solid sponge-like tumor with multicystic areas throughout, in which there were some small hemorrhagic spots, was shown on magnetic resonance (MR) imaging. No endometrial thickening of the uterus was seen. Pathology examination revealed a Sertoli-stromal cell tumor with intermediate-to-poor differentiation. The edematous, watery, sponge-like appearance on the MR images correlated with the pathological findings.