We report a case of left inguinal lymph node metastasis of anal canal carcinoma, treated effectively with chemotherapy consisting of S-1 and CDDP combined with radiotherapy. In February 2006, a 76-year-old woman underwent resection of a tumor diagnosed as squamous cell carcinoma of the anal canal. The patient refused additional surgical therapy. In August 2007, a painful lymphnode swelling was noticed in the left inguinal region. Biopsy was performed, and specimens were shown to include squamous cell carcinoma cells. The patient was treated using chemotherapy concurrent with radiotherapy. The chemotherapy consisted of oral S-1 (80 mg/body/day; 5 days/week) and intravenous CDDP (5 mg/body/day; 5 days/week), both administered for 4 weeks. Radiotherapy at 2 Gy/day was administered 25 times (total dose 50 Gy). The metastatic tumor in the lymph node responded well to the treatment and decreased remarkably in size by December 2007. After chemoradiotherapy, the oral administration of S-1 alone (80 mg/body) for 2 weeks followed by a 2-week rest period as one course was continued for 1 year. The lymph node metastasis had disappeared 1 year after chemoradiotherapy, as determined by computed tomography (CT) and positron emission tomography-CT, representing a complete response. Chemotherapy consisting of S-1 and CDDP concurrent with radiotherapy maybe effective for treating metastatic lymph node metastasis of anal canal carcinoma.