A mattress encasement with improved bed bug protection includes an encasement body configured to cover a mattress and a zipper disposed at an opening in the encasement body and movable between an open condition permitting insertion and removal of the mattress and a closed condition preventing bed bugs from traversing the zipper. The zipper has a zipper head and a zipper pull pivotable on the zipper head. A clasp is at least partly fixed to the encasement body. A hook-and-loop fastener is associated with the encasement body and the clasp for locking the zipper pull to the clasp with the zipper in the closed condition to prevent movement of the zipper head and opening of the zipper.