Abstract: The automatic non-reusable needle guard includes an outer cylinder adaptable to a needle or needle retaining device such as a syringe. An inner cylinder is operable with the outer cylinder for movement of the inner cylinder from an initial retractable position to a released or armed position and further to an extended irreversible position. The mechanism which provides movement of the inner cylinder relative to the outer cylinder incorporates a track formed in the inner surface of the outer cylinder. The inner cylinder incorporates at least one protruding member which may be formed on the outer surface of the inner cylinder and is positioned in the track for guiding the inner cylinder from the initial usable position to the released position and further to the extended irreversible position.