In this work, the optical properties of Au-Ag alloys with an anthracene ligand grafter to their surfaces was examined. Structurally and chemically homogeneous Au-Ag alloy NPs were synthesized by a seed-mediated method with the Ag precursor reduced and grown onto the prepared Au seeds. The alloy NPs were formed after inter-diffusion of Au and Ag and protected using oleylamine. Functionalization of the metal NPs with the anthracene-incorporated ligands was conducted via a simple ligand exchange protocol. The morphological information and chemical composition of the resulting NPs were confirmed by transmission electron microscopy and energy dispersive X-ray spectroscopy, respectively. The plasmonic effect of the metal NPs on the fluorescence was examined using Ultraviolet-visible and fluorescence spectroscopy. The plasmonic enhancement of the fluorescence was found to be varied among different compositions of the alloy NPs.