A seat back cover in the form of a flexible bag of plastic or paper is shaped to fit over the back of a typical folding chair. The seat back cover may include structure to retain the bag on the chair, e.g., against the force of wind in an outdoor setting. The seat back cover may include vertical adhesive strips with peel covers placed on the back of the bag proximal to the chair edges so that if the cover is put on a smaller chair, the sides of the bag can be folded toward the back of the bag and taped out of the way. Multiple bags may be concatenated on a roll and separated by perforations, and the adhesive strips may be placed so as to fold the corners down over the rounded corners of the chair back.