Increasing evidence has revealed that aberrant expression of miRNAs contributes to non-small cell lung cancer (NSCLC) development and progression. However, the roles and mechanisms of various miRNAs in NSCLC remain to be determined. In the present study, we confirmed that reduced miR-212 expression was present in NSCLC tissues and cell lines. Our clinical analysis revealed that the reduced miR-212 expression was significantly correlated with poor prognostic features including positive lymph node metastasis and advanced tumor-node-metastasis (TNM) stage. Moreover, we demonstrated that miR-212 is a novel independent prognostic marker for predicting 5-year survival of NSCLC patients. The ectopic overexpression of miR-212 inhibited cell migration, invasion and EMT, while downregulated miR-212 reversed the effect. In addition, miR-212 regulated SOX4 by directly binding to its 3'-untranslated region (3'-UTR), leading to suppression of EMT progression. In clinical samples of NSCLC, miR-212 was negatively correlated with SOX4, which was upregulated in NSCLC. Alteration in SOX4 expression reversed the functional effects of miR-212 in regards to migration, invasion and EMT in the NSCLC cells. In conclusion, our data indicated that miR-212 functions as a tumor-suppressor gene by regulating EMT and metastasis of NSCLC by targeting SOX4 signaling, and may represent a novel potential therapeutic target and prognostic marker for NSCLC.