A parking assistance system includes a usage status acquisition unit configured to acquire usage status information indicating a usage status at a plurality of parking positions in a parking lot, a moving vehicle information acquisition unit configured to acquire a position of a vehicle moving in the parking lot, a control unit configured to select a parking position for the vehicle in accordance with the usage status information and the position of the vehicle, and transmit guidance image information for guiding the vehicle to the selected parking position, and a projection unit configured to project a guidance image based on the guidance image information onto an inside of the parking lot to present the parking position to the vehicle.