Abstract: A seat back or chair cooling apparatus that cools the back of a user without the need of forced air. The cooling apparatus includes a pocket having an open end and three closed or closable sides. At least one gel pack embodiment is configured to be inserted into the pocket open end. An adjustable belt, housed in a belt pocket and attached to the pocket sides, is deployed to affix the back cooler assembly to a chair back. Hook straps and hooks provide additional attachment points to secure the back cooler assembly to a chair back, and these straps and hooks have separate hook strap and hook storage pockets within the cooling pocket. The cooling pocket can include polyester, fabric or olefin materials, and can also include a mesh backside. Embodiments of the pocket closures in the portable seat or chair back cooler include metal-magnetic button fasteners, button and button-hole fasteners, or Velcro™ hook and loop fasteners.