The aim of this study was to investigate neural precursor cell expressed developmentally down-regulated 9 (NEDD9) expression in human gastric carcinoma (GC) and to explore its clinic significance. NEDD9 expression was detected by immunohistochemistry in GC, their corresponding paracancerous histological normal tissues (PCHNTs), and gastric normal tissues. And this result was further confirmed at the protein and mRNA level by Western blotting and quantitative real-time PCR, respectively. The Kaplan-Meier method and log-rank test were employed to compare the overall survival between NEDD9 low-level expression group and NEDD9 high-level expression group. We ascertained frequently NEDD9 up-regulation in both protein and mRNA levels in GC tissues as compared to PCHNTs and normal controls. Immunohistochemical staining indicated that NEDD9 is higher expressed in GC tissues (102 out of 125, 81.8%) than that in PCHNTs (eight out of 42, 19.05%) and gastric normal tissues (one out of eight, 12.50%). NEDD9 expression levels were closely associated with poor differentiation (P=0.002), venous invasion (P=0.012), invasive depth (P<0.001), preset lymph node metastasis (P=0.023), distant metastasis (P=0.017), and high clinical stage (P=0.005). NEDD9 expression was positively correlated with clinical tumor node metastasis (TNM) stage that implied the more advanced clinical TNM stage corresponding to the higher expression level of NEDD9 (rs=0.467, P<0.001). And we also detected frequently NEDD9 up-regulation in both protein and mRNA levels in GC tissues as compared to PCHNTs. Kaplan-Meier survival analysis showed that high NEDD9 expression exhibited a significant correlation with poor prognosis for gastric cancer patients. Our data suggested that NEDD9 could be used as prognostic molecular marker to be applied in the clinical setting to diagnosis, evaluating patient's outcome (prognosis and recurrence) for GC patients.