Bimetallic nanoclusters Au19Cu30 with chemical composition of [Au19Cu30(C CR)(22)(Ph3P)(6)Cl-2](NO3)(3) (where RC C is from 3-ethynylthiophene (H3C4S-3-C CH) or ethynylbenzene (PhC CH)) has been synthesized. Single X-ray structural analysis reveals that Au19Cu30 has a multishelled core structure of Au@Au-12@Cu-30@Au-6, comprising a centered icosahedral Au-13 (Au@Au-12) surrounded by an icosidodecahedral Cu-30 shell and an outmost shell of a chairlike hexagonal Au-6. The alkynyl carbon is bound to the hollow sites on the Au19Cu30 nanocluster surface, which is a novel interfacial binding mode in alkynyl-protected alloy nano clusters. The Cu-30 icosidodecahedron is unprecedented and Au19Cu30 represents the first alkynyl-protected Au-Cu alloy nanocluster.