Malignant transformation of an ovarian mature teratoma is rare, and it might be diagnosed following laparoscopic surgery in women of reproductive age. Here we report a rare juvenile case of squamous cell carcinoma arising in an ovarian mature teratoma. A 29-year-old woman with a preoperative diagnosis of ovarian mature teratoma underwent single-incision laparoscopic surgery, in which tumor resection was performed extracorporeally following fine-needle aspiration of the cystic contents. Histopathological examination revealed squamous cell carcinoma arising in a mature teratoma of the right ovary. Subsequent right salpingo-oophorectomy and partial omentectomy showed no evidence of a residual malignant component. Because the rate of tumor rupture is significantly higher with the laparoscopic approach than with the laparotomy approach, maximum efforts should be made to avoid intraoperative tumor spillage in cases of an ovarian mature teratoma considering the possibility of unexpected malignancy.