We investigated the effect of multimodal therapy in 187 patients with esophageal cancer. All patients were followed up over a period of 5 years. Among the 187 patients, 174 (93.1%) eligible patients with biopsy-proved esophageal squamous cell carcinoma underwent esophagectomy and were randomly assigned to receive radiotherapy (RT) with or without protein-bound polysaccharide (PSK), or RT plus chemotherapy (CT) with or without PSK. The 5-year survival rates of patients with RT, RT+PSK, RT+CT and RT+CT+PSK were 40.0%, 42.3%, 29.1% and 37.2%, respectively. There was a tendency for longer survival on PSK, but statistical significance was not reached (RT+CT group versus RT+CT+PSK group: log-rank and generalized Wilcoxon tests, P = .1930, P = .1034). However, Cox multivariate regression analysis indicated that postoperative therapy with or without PSK was the most significant prognostic factor for patients receiving RT+CT and for the eligible patients. These results indicate that PSK may have a beneficial effect on esophageal carcinoma when given in combination with CT+RT.