Polymer blends comprises 1) at least one ethylene/.alpha.-olefin interpolymer and 2) at least one polyolefin, or at least one styrenic block copolymer, or a combination thereof. Such polyolefins include, but are not limited to, high melt strength high density polyethylene and high melt strength polypropylene. The ethylene/.alpha.-olefin interpolymers are random block copolymers comprising at least a hard block and at least a soft block. The polyolefins can be homopolymers or interpolymers. The resulting polymer blends can be used to make flexible molded articles.