An alert system for a vehicle includes a video display, an interior visual alert device disposed at an interior rearview mirror assembly, a driver side visual alert device disposed at a driver side exterior rearview mirror assembly and a passenger side visual alert device disposed at a passenger side exterior rearview mirror assembly. A control is operable to activate at least one of the alert devices in response to a detection of an object rearward of the vehicle. The alert devices are viewable by the driver of the vehicle when activated and are operable to guide or prompt the driver to check the images captured by a rearward facing camera and displayed in the vehicle cabin by the video display so that the driver can verify the nature and type of a potential hazard rearward of the vehicle.