Breast cancer-specific gene 1 (BCSG1), also referred to as γ-synuclein (SNCG), is highly expressed in human infiltrating breast carcinomas, but not in normal or benign breast tissue. The present study aimed to evaluate the effects of BCSG1 siRNA delivered by lentiviral vector on breast cancer cells and investigate the underlying mechanisms. BCSG1 RNAi lentiviral vector was constructed and transfected into MDA-MB-231 cells. BCSG1 mRNA levels were determined by quantitative polymerase chain reaction analysis. Cell proliferation, migration and apoptosis were evaluated by using the cell counting kit‑8, Transwell assay and flow cytometry, respectively, followed by western blotting to determine the relative levels of AKT, extracellular signal‑regulated kinase (ERK), p-AKT and p-ERK expression. BCSG1 mRNA levels were significantly reduced in MDA-MB‑231 cells following transfection of BCSG1 siRNA delivered by lentiviral vector. Cell migration and proliferation were significantly decreased and the cell cycle was arrested. Western blot analysis indicated that the protein levels of p-AKT and p-ERK were significantly lower in the BCSG1 siRNA-treated groups compared with the control and negative control groups. Therefore, BCSG1 siRNA delivered by lentiviral vector was able to significantly reduce BCSG1 expression, suppress cell migration and proliferation, possibly through the reduction of the protein levels of p-AKT and p-ERK.