A vehicular driving assist system includes a plurality of cameras disposed at a vehicle and an image processor that processes captured image data. With a trailer equipped with at least one trailer camera hitched to the vehicle, a display screen displays video images derived from captured image data. The system determines a reversing path for the vehicle and trailer to follow to assist the driver in backing up the trailer, and generates a graphic overlay at the display screen that indicates the determined reversing path. During the backing up maneuver of the trailer hitched to the vehicle, and responsive to determination of an object rearward of the trailer, the system (i) determines an adjusted reversing path to avoid the object and (ii) adjusts the graphic overlay to indicate the adjusted reversing path of the vehicle and trailer for the driver to follow in backing up the trailer.