An anti-loose closure, in particular for closing noxious substance containers, such as bottles and the like, wherein the closure comprises a first cap (2), preferably made of aluminium, having, at a lower part thereof, a safeguard strip (4) that is detachable along a break line (5), and, at an upper part thereof, a knurled rim (6); a second cap (9) that is external to the first cap (2), said second cap (9) having a knurled region (12) provided therein, near its bottom wall (11), which is designed to engage with the knurled rim (6) on the cap (2); and resilient means formed on the bottom (11) of the outer cap (9) and designed to interfere with the internal lower wall of the inner cap (2) to hold the knurled regions (6 and 12) in an axially spaced relationship with one another, said resilient means being such that when acted upon by an externally exerted pressure they will yield to cause said knurled regions to be brought into mutual engagement.