The adsorption energies and structures of methanethiolate, SCH3, on the (111) surfaces of Au, Ag, and Cu have been studied using a density functional theory. The results obtained for the Au surface are in good agreement with experiments and previous calculations. The strength of the adsorption energies is found to be Cu > Ag > Au, and the nature of the chemisorption bond is discussed. The strong interaction between the SCH3 and Cu surface can be explained in a similar way to that as for the binding energy of SCH3 with metal atoms. Scalar-relativistic effects in the adsorption energies and adsorption structures, which dominate the differences observed between the Ag and Au surfaces, are studied using quasirelativistic and nonrelativistic pseudopotentials. The relativistic effects decrease the adsorption energy of SCH3 on the Au(111) surface, although the binding energy of the AuSCH3 complex is increased by relativity. The unexpected relativistic effects are also discussed.