Gastric cancer (GC) is one of the most common malignant cancers worldwide. However, little is known about the molecular process by which this disease develops and progresses. This study investigated correlations between the expression of nuclear transcription factor SOX4 and various clinicopathologic parameters as well as patients' survival. Expression levels of nuclear SOX4 were analyzed by immunohistochemistry; the data comprised gastric tissues from 168 patients with GC. Paired t tests were used to analyze the differences in nuclear SOX4 expression between tumor and non-tumor tissues from each patient. Two-tailed Χ(2) tests were performed to determine whether the differences in nuclear SOX4 expression and clinicopathologic parameters were significant. Time-to-event endpoints for clinicopathologic parameters were plotted using the Kaplan-Meier method, and statistical significance was determined using univariate log-rank tests. Cox proportional hazard model was used for multivariate analysis to determine the independence of prognostic effects of nuclear SOX4 expression. Overexpression of nuclear SOX4 was significantly correlated with depth of invasion (P<0.0001), nodal status (P=0.0055), distant metastasis (P=0.0195), stage (P=0.0003), and vascular invasion (P=0.0383). Patients who displayed high expression levels of nuclear SOX4 achieved a significantly poorer disease-free survival rate, compared with patients with low SOX4 expression levels (P=0.003). Univariate Cox regression analysis showed that overexpression of nuclear SOX4 was a clear prognostic marker for GC (P=0.004). Overexpression of nuclear SOX4 can be used as a marker to predict the outcome of patients with GC.