An auxiliary luggage attachment and security tether mechanism secure an auxiliary luggage case to a main luggage case for support on and by an exterior surface of a main luggage case, and secure at least the main luggage case to an object. The attachment mechanism comprises a clutch mechanism, an elongated flexible strap having an inner end fixably attached to the clutch mechanism and the outer end attached to a hook, the clutch mechanism being biased to pull the flexible strap onto the clutch mechanism and retract the hook to the clutch mechanism. A lid is pivotally mounted adjacent to the clutch mechanism and has a selectively open position where the hook and strap are accessible, and a selectively closed position where the lid covers the clutch mechanism and the strap or hook to the extent the strap is retracted onto the clutch mechanism. The lid engages the clutch mechanism in the open position to release the clutch mechanism whereby the strap can be extended from the clutch mechanism. The lid engages the clutch mechanism in the closed position to hinder the movement of the clutch mechanism and fix the length of extension of the strap. A lock mechanism in the lid locks the lid in the closed position, covering the clutch mechanism. The hook at the end of the strap can be replaced in the receptacle to engage the clutch mechanism, and the lid can then be locked to secure the hook and the strap to the clutch mechanism.