Surface wettability, one of the most important parameters for oil–water separation, depends on the chemical composition and surface roughness of a material. Herein, the Pickering emulsion template method is proposed to control the surface wettability of polymer microspheres. Upon the dispersion of modified diatomite particles in the aqueous phase, a superhydrophobic surface was formed on the polymer microspheres via Pickering emulsion polymerization, with a water contact angle of 152°. When the initial dispersion location of the modified diatomite particles changed from water to oil, a hydrophilic/underwater superoleophilic surface with micro/nanoscale hierarchical structures formed on the polymer microspheres. This special wettability enabled the microsphere layer to serve as an adsorbent with underwater superoleophilicity, achieving efficient oil separation from various oil-in-water emulsions with high separation efficiency of >99.8%. Hence, this study provides a valuable strategy based on the Pickering emulsion template method to design materials with special wettability for realizing promising emulsion separation.