Abstract: A chimney screen device for covering the open end of a chimney to prevent access into the chimney by squirrels, birds and the like includes a rigid frame sized and constructed to be disposed upon and about an exposed end of a chimney flue liner, the frame defining an opening corresponding with the open end of the chimney flue. The device further includes a mesh of metallic material attached to the frame about the opening and spanning the opening, the mesh defining a plurality of apertures of grid size selected to prevent access of squirrels, birds and the like therethrough and having open area of at least 90% for passage of hot gases from the chimney flue therethrough without significant detrimental effect upon chimney draft, and fasteners for engaging upon outer walls of the flue liner for fixing the frame upon and about the end of the chimney flue liner, with the mesh spanning the open end of the chimney flue liner.