Abdominal wall endometriosis represents 1-2% of all endometriotic lesions. The malignant transformation of abdominal wall endometriosis is rare, though it can occur. Herein the authors report a rare case of clear cell adenocarcinoma arising from abdominal wall endometriosis with extensive lymph node metastasis. In this case, a 51-year-old woman presented with a growing mass in the right periumbilical area. Computed tomography scan revealed a 5-cm solid mass located on the right rectus muscle. A punch biopsy of the abdominal lesion was performed and histology showed metastatic adenocarcinoma of unknown origin. She had a surgical history of laparoscopic subtotal hysterectomy with right salpingo-oophorectomy. The patient underwent radical excision of the mass, trachelectomy, left salpingo-oophorectomy, and lymph node dissection. The abdominal wall mass showed clear cell adenocarcinoma arising from endometriosis on histology. There were extensive lymph node metastases. The patient underwent adjuvant chemotherapy. Both lymphatic and local invasion are key routes of clear cell adenocarcinoma arising from abdominal wall endometriosis. Extensive lymph node metastasis could be associated with poor prognosis.