BACKGROUND To evaluate the feasibility and efficiency of definitive concurrent chemoradiotherapy (dCRT) with S-1 and cisplatin for elderly esophageal squamous cell carcinoma (ESCC) patients. METHODS Fifty-six elderly patients were included from January 2012 to December 2014. Patients received S-1 (tegafur/gimeracil/oteracil) and cisplatin at doses of 70 mg/m2/day for two weeks and 75 mg/m2 on day 1, respectively, every 3 weeks. Radiotherapy was delivered at a dose of 180-200 cGy per day to a total dose of 54 Gy. After dCRT, additional chemotherapy was administered for two cycles. RESULTS The median age was 74 years (range: 70-87 years) and 38 (67.9%) patients were staged with III-IVa. Totally, 38 patients completed dCRT as planned. An objective response rate (ORR) was seen in 47 (84.0%) patients. The median OS and PFS time were 18.2 and 13.9 months and the 3-year OS and PFS rates were 30.1% and 14.2%, respectively. The most frequent hematological toxicities were leucocytopenia and neutropenia with the incidence of 55.4% and 53.6%, respectively. A significantly higher incidence of severe leucocytopenia was observed between patients aged ≥75 and 70≤ age <75 years. The most common non-hematologic toxicity was esophagitis. CONCLUSIONS dCRT with S-1 and cisplatin yielded satisfactory survival outcomes but treatment-related toxicities were relatively high, especially for patients aged over 75 years.