The effect of dispersion corrections at a range of theory levels on the chemisorption properties of metallic nanoparticles is presented. The site preference for CO on Pt, Au, Pd, and Ir nanoparticles is determined for two geometries, the 38-atom truncated octahedron and the 55-atom icosahedron using density functional theory (DFT). The effects of Grimme's DFT-D2 and DFT-D3 corrections and the optPBE vdW-DF on the site preference of CO is then compared to the "standard" DFT results. Functional behavior is shown to depend not only on the metal but also on the geometry of the nanoparticle with significant effects seen for Pt and Au. There are both qualitative and quantitative differences between the functionals, with significant energetic differences in the chemical ordering of inequivalent sites and adsorption energies varying by up to 1.6 eV.