Abstract: A dress cover installable over a seatback of a passenger seat and having an integrated adjustable lumbar support device is disclosed. In embodiments, the dress cover includes a fabric outer shell and a seat cushion within the outer shell. The lumbar support device is disposed inside a pocket set into the dress cover and corresponding to the lumbar area of the seat occupant. The pocket extends laterally between left-side and right-side slots, each slot held closed by a zipper within which a slider tracks up and down to adjust the lumbar support device. As the slider tracks along the zipper it opens and closes the zipper within the body of the slider, maintaining its slot in a closed configuration. By adjusting the sliders up or down, the occupant may adjust the position of the lumbar support device through the dress cover.