Abstract: A sleeve for use by baseball or softball pitchers is provided. The sleeve covers the entirety of the arm and shoulder and is easily slipped on and off. Pitchers can thereby keep their pitching arm warm by wearing the sleeve between innings. Alternatively, pockets or other securing means are provided whereby a wearer can add a heating or cooling pad or bag so that the arm can be warmed or cooled. The sleeve is also useful for purposes other than keeping a pitching arm warm. For example, an arm that is sore from muscle strain or after an operation can be cooled by using cold packs in the sleeve so that swelling is minimized.