A vehicle power supply system is provided. The system includes a first power line connected by a first inverter and a first battery, a second power line connected by a second inverter and a second battery, a voltage converter, and a charging and discharging control device operating the inverters and the voltage converter. The control device charges the second battery with second regenerative electric power that is power supplied from the second inverter to the second power line in a case where a second SOC is equal to or less than the second regeneration permission upper limit during regenerative deceleration, and prohibits the second battery from being charged and supplies at least a portion of the second regenerative electric power to the first battery through the voltage converter and the first power line when the second SOC is larger than the second regeneration permission upper limit.