Abstract: A cap for a chimney is provided. The cap comprises a heat resistant cover, having a topside and an underside, extending across the chimney in superposed and spaced relation thereto. A support means is attached to the underside of the cover for supporting the cover in superposed and predetermined spaced relation above the chimney. A plurality of adjustable detachable mounting means are attached to the support means for detachably mounting the cover to the chimney. The mounting means are adjustable to accommodate the opening in the chimney. A particular advantage of this cap is that it can be easily installed in variously sized chimneys, and is of simple and inexpensive construction. Additionally the cap has a novel heat resistant cover.