Abstract: The improved portable auxiliary seat cushion with upper body support for children is described as an elongated mat comprising four layers; the front and the back layers which are composed of a durable machine washable fabric, and the interfacing and fiber filled layers which are interposed between the front and back layer. The four layers are peripherally interconnected into a unitary structure by a continuous stitching at the perimeters thereof. A straight stitch at the hinge defines a back rest and seat portion. Slits, one on each side below the hinge, provide slots for seat belt. An upper body support ridge comprises five parts: The support ridge filler, which is made of a firm, yet resilient, material; the outermost, innermost, and uppermost sections; and the bottom ends, which create a tubular form. A zipper is attached centrally to the outermost section for easy removal of the ridge filler to facilitate laundering.