A handgun holster with an accessory mounting block and a holster locking device are disclosed. The holster locking device may be mounted on the holster. The holster locking device includes a member for securing a rear end of a handgun. The holster locking device includes a frame. The interior surface of the frame may comprise first and second guide members such that the first and second guide members may be disposed in first and second guide grooves in the holster accessory mounting block. Also disclosed is a passage in the frame. A cantilever on the holster accessory mounting block may be disposed in the passage to engage the frame and lock the handgun holster to the holster locking device.