A vehicular trailering assist system includes a camera disposed at a rear portion of a vehicle. With a trailer hitched to the vehicle at a hitch ball of the vehicle, the camera views at least a portion of the trailer. An electronic control unit includes an image processor operable to process frames of image data captured by the camera. With the trailer hitched to the vehicle at the hitch ball of the vehicle, the vehicular trailering assist system determines trailer feature points via image processing of image data captured by the camera, and determines respective perpendicular bisectors of respective line segments extending between the determined trailer feature points in respective frames of captured image data while the vehicle tows the trailer and turns. The vehicular trailering assist system determines a location of the hitch ball based at least in part on an intersection point of the determined perpendicular bisectors.