We report findings of magnetic resonance imaging including susceptibility-weighted imaging (SWI) of the subacute torsion of an ovarian fibrothecoma in a patient with renal dysfunction. Although venous thrombosis within the vascular pedicle mimicked a malignant tumor, showing high signal intensity on T₂-weighted images and diffusion-weighted imaging, we diagnosed ovarian torsion on SWI without the administration of contrast medium, aided by the prominent susceptibility-induced signal void caused by the thrombosis.