As one of the most common malignancies, esophageal squamous cell carcinoma (ESCC) is ranked as the sixth leading cause of cancer-related death worldwide. In our previous study, by employing cDNA microarray analysis, semaphorin 3B (SEMA3B) was found to be significantly downregulated in ESCC. In the present study, SEMA3B downregulation at the mRNA level was found in 34 of 60 primary ESCCs (56.7%) and in 6 of 9 ESCC cell lines (66.7%) by transcription-polymerase chain reaction (RT-PCR). Moreover, immunohistochemical (IHC) staining of SEMA3B in a tissue microarray further indicated that downregulated expression of SEMA3B protein was found in 125 of 222 (56.3%) ESCC cases and downregulation of SEMA3B protein was significantly correlated with lymph node metastasis (P=0.000), advanced clinicopathological stage (P=0.001) and poor disease-specific survival (P=0.017) of ESCC patients. In addition, functional studies demonstrated that the SEMA3B gene could suppress the tumorigenic ability of ESCC cells and cell motility. Furthermore, it was found that by upregulating p53 and p21 expression and inhibiting Akt (Ser473) phosphorylation, SEMA3B could induce cell cycle arrest at G1/S phase. Taken together, our results suggest that SEMA3B may be an important tumor-suppressor gene in the malignant progression of ESCC, as well as a valuable prognostic marker for ESCC patients.