A protective cover for a zone of a machine tool, in which a machining part moves along an operating path, preferably extending on a single plane, in said zone; the cover comprises a plurality of cover elements consisting of a fixed cover element which can be fixed to the machine, a mobile element connected to the machining part and a plurality of mobile cover elements positioned between the fixed cover element and the mobile cover element which is connected to the machining part; the cover elements are closed in a pack, each with a window, and are arranged according to decreasing size and lie around the machining part, connected to one another by a first and a second support rod, at a given distance from one another and with respective mobile cursors on the rods so as to guide the mobile cover elements in a direction parallel with and a direction at right angles to the rods, during movement of the machining part, keeping the machining zone covered.