A vehicle control system comprising: an external information acquiring device configured to be capable of acquiring presence of a preceding vehicle located in front of a vehicle and an inter-vehicular distance between the vehicle and the preceding vehicle; a vehicle speed acquiring device configured to be capable of acquiring a traveling speed of the vehicle; and a control device configured to be capable of executing adaptive cruise control of the vehicle, in the adaptive cruise control, the vehicle is controlled to maintain an acquired value of the inter-vehicular distance (b) acquired by the external information acquiring device at a predetermined inter-vehicular distance set value when the external information acquiring device acquires information indicating the presence of the preceding vehicle, and the vehicle is controlled to maintain an acquired value of the traveling speed acquired by the vehicle speed acquiring device at a predetermined traveling speed set value when the external information acquiring device does not acquire the information indicating the presence of the preceding vehicle, wherein: the control device is configured to be capable of calculating a poor visibility degree (d) for evaluating poor visibility in front of the vehicle; and the control device is configured to disenable acceleration of the vehicle and permit constant speed traveling of the vehicle in the adaptive cruise control when a calculated value of the poor visibility degree (d) is equal to or greater than a predetermined first poor visibility degree threshold. an external information acquiring device configured to be capable of acquiring presence of a preceding vehicle located in front of a vehicle and an inter-vehicular distance between the vehicle and the preceding vehicle; a vehicle speed acquiring device configured to be capable of acquiring a traveling speed of the vehicle; and a control device configured to be capable of executing adaptive cruise control of the vehicle, in the adaptive cruise control, the vehicle is controlled to maintain an acquired value of the inter-vehicular distance (b) acquired by the external information acquiring device at a predetermined inter-vehicular distance set value when the external information acquiring device acquires information indicating the presence of the preceding vehicle, and the vehicle is controlled to maintain an acquired value of the traveling speed acquired by the vehicle speed acquiring device at a predetermined traveling speed set value when the external information acquiring device does not acquire the information indicating the presence of the preceding vehicle, wherein: the control device is configured to be capable of calculating a poor visibility degree (d) for evaluating poor visibility in front of the vehicle; and the control device is configured to disenable acceleration of the vehicle and permit constant speed traveling of the vehicle in the adaptive cruise control when a calculated value of the poor visibility degree (d) is equal to or greater than a predetermined first poor visibility degree threshold. the control device is configured to be capable of calculating a poor visibility degree (d) for evaluating poor visibility in front of the vehicle; and the control device is configured to disenable acceleration of the vehicle and permit constant speed traveling of the vehicle in the adaptive cruise control when a calculated value of the poor visibility degree (d) is equal to or greater than a predetermined first poor visibility degree threshold.