Recently, it is reported that a omega-3 fatty acid-containing diet (Racol) enhances innate immunity and reduces mucosal damage in the small intestine during chemotherapy. The aim of this study is to examine the effects of a omega-3 fatty acid-containing diet (Racol) on the toxicity of chemoradiation therapy (CRT) for patients with esophageal cancers. Toxicity of CRT was evaluated in 10 patients who took Rakol at a maximum dose of 600 mL/day during CRT, compared with 10 patients who did not take Rakol. Regarding blood toxicity, the decrease of platelets did not differ between the former and the latter. However, the incidence of grade 2~4 neutropenia was lower in the former than in the latter (p=0.0043). With regard to gastrointestinal toxicity, the incidence of grade 2~4 diarrhea was also lower in the former than in the latter (p=0.0118). Moreover, the incidence of grade 2~4 stomatitis/pharyngitis tended to decrease in patients who took Rakol compared with those who did not (p=0.0812). The current results indicated that a omega-3 fatty acid-containing diet (Racol) may be beneficial to patients with esophageal cancers who receive CRT by reducing CRT toxicity.