A vehicular trailer angle detection system includes a rear camera, a left-side camera, a right-side camera and a control having an image processor. With a trailer hitched at a vehicle, and while the vehicle is driven in a forward direction and towing the trailer, image data is captured by at least one of the cameras. The vehicular trailer angle detection system determines an expected location of the portion of the trailer based on provided vehicle-trailer parameters as the vehicle is driven forward and towing the trailer. The vehicular trailer angle detection system determines an actual location of the portion of the trailer via processing of captured image data as the vehicle is driven forward and towing the trailer. Responsive to an offset between the determined actual location of the portion of the trailer and the determined expected location, the vehicular trailer angle detection system accommodates the offset.