A novel mixed micelle with a multifunctional core and shell is successfully prepared from a graft copolymer poly(N-isopropyl acrylamide-co-methacrylic acid)-g-poly(D,L-lactide) (P(NIPAAm-co-MAAc)-g-PLA) and two diblock copolymers, poly(ethylene glycol)-b-poly(DL-lactide) and poly (2-ethyl-2-oxazoline)-b-poly(D,L-lactide). This nanostructure completely screens the highly negative charges of the graft copolymer and exhibits multifunctionality because it has a specialize core/shell structure. An example of this micelle structure used in intracellular drug delivery demonstrates a strong relationship between drug release and the functionality of the mixed micelle. Additionally, the efficiency of the screening feature is also displayed in the cytotoxicities, mixed micelles exhibit higher drug activity and lower material cytotoxicity than micelles from P(NIPAAm-co-MAAc)-g-PLA ([NIPAAm]/[MAAc]/[PLA]-84.5.9.2.5 mol/mol) copolymer. This study not only presents a new micelle structure generated using a graft-diblock copolymer system, but also elucidates concepts upon which the preparation of a multifunctional micelle from a graft copolymer with a single (or many) diblock copolymer(s) can be based for applications in drug delivery.