Abstract: An anti-theft door lock comprised generally of two sections, an outer spring loaded section and an inner section connected to the door locking mechanism in which the outer section is pushed downwardly exposing the inner section which can then be manipulated like a conventional door lock to either lock or unlock the car door.The anti-theft device is used as a replacement unit for the one originally supplied with the vehicle. It can be placed in the door sill without the need of any tools and is designed to be screwed onto the existing locking rod which actuates the door lock. Because of the inherent design features, the door lock cannot be actuated by the use of wire type devices, such as coat hangers by would-be car thieves.