The effect of adsorbed S on the adhesion of Fe(l 10) surfaces is examined using density functional theory. Adsorption of S in the hollow, bridge, and atop sites is modeled at a 1/4 monolayer coverage in match and mismatch interfaces. The calculated adhesion energy curves and fitted universal binding energy relation (Rose et al. Phys. Rev. B. 1983, 28, 1835) show that the presence of S on the surface reduces the strength of the interface. The effect of adsorbed S on the charge density distribution and magnetic properties of the interface are also examined and can be related to the interfacial geometry. The effect of relaxation of the interfaces at equilibrium is also investigated and is shown to increase the strength of the interface, while reducing the equilibrium interfacial separation.