Abstract: An anti-tamper container closure assembly includes a container having a orifice defining neck which receives a closure cap. The container has a plurality of projecting anti-rotation teeth positioned below the bottom of the closure cap and an overcap is adapted to be snapped over the closure cap, the overcap having a skirt with inner diameter projecting anti-rotation ribs which index with the container teeth to prevent rotation of the overcap. The overcap is effective to prevent opening of the orifice and is provided with frangeable connecting portions allowing a part of the overcap to be removed from the assembly to provide access to the closure cap for an opening actuation of the closure cap. The overcap skirt is provided with an inner diameter ledge which abuts a closure cap outer diameter ledge to prevent removal of the overcap skirt.