Provided is a composition which can be utilized for drug delivery systems that can penetrate the blood brain barrier, and has low cytotoxicity. A nanoparticle composition comprises nanoparticles to the surface of which a first substance and a second substance each having specificity to a tumor cell are bound, wherein the first substance having specificity to the tumor cell is a peptide comprising an amino acid sequence of arginine-glycine-aspartic acid, and wherein the second substance having specificity to the tumor cell is an iron-binding protein, and wherein the nanoparticles each comprise an outer layer and vesicles enveloped by the outer layer and the nanoparticles each comprise, as membrane components, a PEGylated phospholipid, a fatty acid with a melting point of 30° C. or more, and a non-PEGylated phospholipid.