The interaction of molecular S2with cleaved GaAs(110) surfaces was followed by using a Kelvin probe and ultraviolet photoemission spectroscopy. The adsorption of sulfur increases the ionization energy of the cleaved surfaces by up to 0.92 eV and causes a Fermi‐level pinning at 0.34 eV above the valence‐band top for both types of doping. The sign of the change of the ionization energy can be explained by a chemical charge transfer between the adsorbed sulfur and adsorbate‐induced gap states, since sulfur is more electronegative than GaAs. The sulfur‐related pinning position of the Fermi level is located below the charge‐neutrality level of the virtual gap states (ViGS) of the complex GaAs band structure, where the ViGS predominantly possess donor character. This result confirms the predictions from the ViGS model of adsorbate‐induced gap states. The energy of the sulfur as well as the oxygen‐ and chlorine‐related surface states, which are of the acceptor type, correlate with the respective atomic electron affinities.