A control system for a plug-in hybrid vehicle includes a drive system including a starter motor, a transverse engine, and a motor/generator, and a power supply system including a high voltage battery, a capacitor, and a hybrid control module that controls charging and discharging of the capacitor. In the control system for an FF plug-in hybrid vehicle in which an external charging of the high-power battery is available, the hybrid control module starts the starter, performs mode selection control and charge/discharge control, maintains a capacitor voltage at or below a deterioration free voltage when the CS mode is selected during ignition on, and recharges the capacitor to a starter start-up permission voltage that allows the starter to start when a pre-forecast of the reverse transition from the CS mode to the CD mode is established.