A thin Pt layer supported on tin (Sn) is suggested as a catalyst with greater CO tolerance for fuel cell anode applications. DFT calculations of the adsorption energy of one CO molecule on one Pt monolayer supported on seven monolayers of Sn show significantly higher values (-1.04 eV/molecule), in comparison with the adsorption energy on 2, 3, and 5 monolayers and metallic Pt(111) (-1.82 - -1.92 eV/molecule). For full CO coverage, the adsorption energy is larger (less negative) in comparison with monometallic Pt (-0.93 eV/molecule) for one (-0.55 eV/molecule) and even two monolayers (-0.83 eV/molecule). Correlation between E ads-adsorption energy and Pt d-band center (ϵ d) was found for full coverage of CO. Cyclic voltammetry supports the conclusion that CO is weakly bound on a thin Pt layer coated on metallic Sn. Unlike CO adsorption, methanol adsorption energies on Pt are not affected by the supporting tin (-0.695 eV/molecule for MeOH/Pt1/Sn7 in comparison to -0.690 eV/molecule for MeOH/Pt). Thus, a very thin layer of Pt supported on Sn can prevent CO adsorption and may function as an effective catalyst for fuel cells.