Adsorption of Ba and its effect on the GaAs(110) surface oxidation has been studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The Ba adsorption onto the surface results in a disordered interface of Ba and the GaAs surface at temperatures <500 °C. However, the reactivity of the GaAs surface to oxygen is dramatically enhanced by the adsorbed Ba atoms. This enhancement of the surface oxidation is proportional to the Ba exposure. Study of LEED and AES intensities has also revealed evidence of Ba‐induced surface disorder on the GaAs.