The invention relates to a method for operating a motor vehicle when changing lanes on a roadway consisting of at least three lanes, with the steps: detection by a monitoring system in the vehicle of an impending lane change of the motor vehicle from a first lane to an adjoining second lane; detection of an impending lane change by another vehicle from a third lane that adjoins the second lane, to the second lane; the monitoring system determining whether a collision with the other vehicle threatens if the vehicle changes lanes; as soon as a threatened collision is determined, a warning signal is issued by a warning device and/or the motor vehicle is influenced in its lateral motion by a driver assistance system of the vehicle. In addition, it relates to a motor vehicle with a monitoring system.