Sclerosing stromal tumor (SST) of the ovary is a very rare sex cord stromal tumor occurring in a younger age group than other types of stromal tumors and most commonly accompanied by menstrual irregularity. Several unique histologic features including pseudolobulation, sclerosis and prominent vascularity are clearly reflected at ultrasonography and MRI. We report the ultrasonographic and MR features of three cases of histologically confirmed SSTs, and relate them to the pathological findings.