Objective To study the effects of α-synuclein overexpression on SH-SY5Y cells treated with rotenone. Methods Human dopaminergic SH-SY5Y cells were transfected with α-synuclein-EGFP and selected by antibiotics. After treatment with rotenone at different concentrations, both native and α-synuclein-overexpressed SH-SY5Y cells were collected and used for detecting the cell viability, reactive oxygen species and antioxidant capacities of cells. Results The decreased cell viability and increased oxidative stress were observed in cells treated with rote- none. However, higher levels of cell viability and antioxidant capacities were found in α-synuclein overexpressed cells when compared to those in native SH-SY5Y cells (P<0.01). Conclusion α-synuclein overexpression partially protects cells against rotenone insult by increasing cell viability and antioxidant capacities in SH-SY5Y cells.