A sex cord tumor with annular tubules (SCTAT) is a rare but distinctive subtype of sex cord stromal tumor of the ovary. Its clinical features depend on an association with Peutz-Jeghers syndrome (PJS). SCTAT associated with PJS typically manifests as bilateral, multifocal, and small lesions and is clinically benign. In contrast, SCTAT not associated with PJS often manifests as a unilateral large mass and 20% of such tumors have malignant potential. Most patients with SCTAT are diagnosed at stage I, and metastasis is rare. Here we present a case of malignant SCTAT of stage III A1(ii) (retroperitoneal lymph node metastasis, largest dimension of metastasis >10 mm) in a 14-year-old girl without PJS.