A method and a device for warning the driver of a motor vehicle. An object detector is provided, which detects preceding vehicles and ascertains their distance and relative velocity with respect to the host vehicle and supplies these to an evaluation device. The evaluation device assumes that the preceding vehicle would perform a deceleration and ascertains as a further function of the variables measured by the object detector and the driver's reaction time and the host vehicle's maximum possible deceleration whether a collision with the preceding vehicle would be avoidable. If an unavoidability of a collision is recognized, then a driver warning device is activated.