Developing efficient methods to improve catalytic selectivity, particularly without sacrificing catalytic activity, is of paramount significance for chemical synthesis. In this work, we report a small ligand-involved Pickering droplet interface as a brand-new strategy to effectively regulate reaction selectivity of metal catalysts. It was found that small ligands such as polar arenes could engineer the surface structure of Pt catalysts that were assembled at Pickering droplet interfaces. Due to the strong hydrogen-bonding interactions with water, the polar arenes preferentially adsorbed with the water adlayer that covered Pt surfaces, forming water-mediated metal-organic interfaces on the Pickering emulsion droplets. Such an interface system displayed a significantly enhanced