A zipper carton includes a first panel having an elongated slot extending therethrough, the slot having a length extending between opposing ends. A locking panel assembly includes a removable zipper tear strip and a locking tab having a linear length that is greater than the length of the slot. The locking tab includes a base projecting from the removable zipper tear strip and a first retention flap projecting from the base and being foldable relative to the base. The locking tab is configured so that when the first retention flap is folded from a relaxed position to a folded position, at least a portion of the locking tab including the first retention flap can be slid through the slot and after the first retention flap passes through the slot, the retention flap automatically resiliently rebounds at least partially toward the relaxed position so as to block retraction of the locking tab from the slot.