Desmoplastic small round cell tumor (DSRCT) is a rare, but highly aggressive primary peritoneal malignancy, and predominantly affects the male adolescent. It has a very poor prognosis despite multimodal therapy. We report an uncommon case of a 12-year-old female patient who presented with progressive abdominal distension associated with poor appetite and weight loss, and was subsequently diagnosed as DSRCT based on imaging and histological analysis with positive immunohistochemical staining for Wilms' tumor 1 protein.