This case report describes a successful treatment of rare double malignant fistulas in an advanced rectosigmoid junction tumor using neoadjuvant chemoradiation and surgery. An 81 year old woman presented with poor appetite, abdominal fullness, dizziness, and bloody stool. She was diagnosed with an advanced rectosigmoid junction tumor with double malignant fistulas (ceco sigmoid and ileo sigmoid fistulas). The patient received neoadjuvant chemoradiation therapy followed by surgical resection of the tumor and the fistulas. The patient’s postoperative recovery was uneventful. Her pathological examination showed a partial pathological response to the neoadjuvant therapy. The patient had no evidence of local recurrence or distant metastasis at her 1 year follow up. This case demonstrates the importance of a multidisciplinary approach in managing complex cases and suggests that neoadjuvant chemoradiation therapy combined with surgery may be an effective treatment for advanced rectosigmoid junction tumors with double malignant fistulas.