Abstract: A trailer back-up mirror which can be-removably attached to the frame of a boat, camper, recreational vehicle or other trailer for facilitating alignment of the hitch ball on a towing vehicle with the trailer hitch as the vehicle is backed toward the trailer, in order to couple the trailer hitch to the hitch ball. In a preferred embodiment the trailer back-up mirror is characterized by a support shaft which is magnetically and removably attached to the trailer frame. An adjusting shaft is adjustably extendible from the support shaft and a flexible gooseneck shaft extension projects from the extending end of the adjusting shaft. A rectangular mirror mount plate terminates the shaft extension and a flat mirror and convex mirror are mounted on the mirror mount plate. In use, the gooseneck shaft extension is initially adjusted to position the mirror mount plate such that the trailer hitch and hitch ball appear in the convex mirror, and the trailer hitch appears in the flat mirror.