Synuclein-γ (SNCG), a synuclein family member, promotes migration, invasion and metastasis of tumor cells; however, the mechanism remains unclear. The present study investigated the effect of SNCG on malignant phenotypes of MCF7 cells using cell proliferation analysis, cell migration assays and wound healing assays, and verified its effects on extracellular‑signal regulated kinase (Erk) activation and epithelial to mesenchymal transition‑related markers using western blotting. The results indicated that SNCG increased migration (P<0.05) but not proliferation (P=0.711) of MCF7 cells. It was also demonstrated that SNCG activated the Erk pathway and an inhibitor of Erk signaling significantly counteracted SNCG‑induced migration. Furthermore, it was shown that SNCG downregulated levels of tight junctions‑associated factors E‑cadherin and ZO‑1, while inhibiting the Erk pathway did not affect their levels. In conclusion, SNCG may promote MCF7 cell migration through activating the Erk pathway and breaking cell-cell junctions.