A driver assistance system for vehicles, which is capable of preventing driver carelessness from causing a vehicle accident when a vehicle stops while traveling, includes a vehicle sensor unit configured to detect driver state data, a driver assistance unit operated to assist a driver when driver carelessness about vehicle driving is detected when a vehicle stops while traveling, and a control unit configured to identify whether the driver is careless based on the driver state data when the vehicle stops while traveling, and to operate the driver assistance unit when the driver carelessness is detected, preventing the vehicle from driving.