A vehicle control system including a mobile device and an onboard device is provided. The onboard device performs vehicle control when the onboard device receives an authentication code from the mobile device located within an effective area. The mobile device measures reception strength of a vehicle signal from the onboard device and stores strength information indicating characteristics of the reception strength corresponding to a target distance to the onboard device. The mobile device determines whether or not the mobile device is located within an effective area, based on the reception strength and the strength information. The mobile device acquires correction information indicating characteristics of the reception strength corresponding to a mobile state quantity and corrects the strength information based on the mobile state quantity and the correction information.