MicroRNA-7 has been reported to participate in tumorigenesis and progression by several signaling pathways in various tumors. However, its potential as a serum diagnostic factor and predictive biomarker for esophageal squamous cell carcinoma (ESCC) has not been studied. Serum samples were collected from 105 pathologically proven ESCC patients and 30 age- and gender-matched healthy controls. All patients were treated with concurrent chemoradiotherapy (CRT). Real‑time polymerase chain reaction was carried out to measure the serum miR-7 expression level. The data were compared among radio-sensitive and radio-resistant groups, and healthy volunteers to elucidate the diagnostic and predictive value of miR-7 expression. Finally, in vitro experiments are used to clarify the mechanisms of the miR-7. In the present study, we found that the serum miR-7 level of ESCC patients was 4.74-fold lower as compared with healthy subjects, indicating that serum miR-7 expression could be an excellent diagnostic factor. The serum miR-7 expression level for these responsive patients was 2.34‑fold higher than that for non-responsive patients, indicating it as a valuable biomarker for predicting treatment response of ESCC patients to concurrent chemoradiation treatment. We also found that miR-7 levels are strongly correlated with tumor length and the status of lymph node metastasis (P<0.05). In contrast, the responsiveness of therapy is significantly correlated with CEA (P<0.05), Cyfra21-1 (P<0.05), serum miR-7 level (P<0.05) and myelosuppression (P<0.01). In addition, the experimental data also suggest that miR-7 can interfere with EGFR mRNA translation. In ESCC patients, serum miR-7 has the potential to serve as a noninvasive biomarker of diagnosis and predicting treatment responses to concurrent chemoradiation therapy. ESCC patients with lower Cyfra21-1 and CEA, higher miR-7 and severe myelosuppression were much more sensitive to CRT. In addition, miR-7 may function by interfering with EGFR mRNA translation, but not degradation.