A vehicular trailer hitching assist system includes a rearward-viewing camera disposed at a vehicle and viewing a hitch of the vehicle and a trailer coupler of a trailer that is positioned rearward of the vehicle and not coupled to the hitch of the vehicle. The vehicular trailer hitching assist system, via image processing of image data captured by the rearward-viewing camera, determines height of the trailer coupler relative to the hitch of the vehicle. The vehicular trailer hitching assist system, responsive to the determined height of the trailer coupler relative to the hitch of the vehicle being greater than a threshold amount, generates a signal to adjust the height of the trailer coupler.