The integration of nanometer-sized fillers into polymer matrices to create nanocomposite materials has attracted a great deal of interest, not only because these materials can be tailored to specific practical applications but also because they can exhibit synergistic combinations of properties that display multifunctionality. Herein, we successfully incorporated silica (SiO2) nanoparticles into the rubber-modified polybenzoxazine (PBZ) by mixing and applied as a nanocomposite coating that exhibits both superhydrophobicity and superoleophilicity through a facile dipping and spraying technique. We used PBZ, not only because of its near-zero shrinkage upon polymerization, chemical resistance, and good dielectric, thermal, and mechanical properties but also because, most importantly, of its low surface free energy and low water absorptivity. With superhydrophobicity coexisting with superoleophilicity in one material, potential anticorrosion, anti-ice, and organics/water separation applications of the coating were investigated. Results revealed that the rubber-modified PBZ coating with the optimum SiO2 loading was able to display superior antiwettability and anticorrosion performance even during prolonged exposure to corrosive environment. The coating also showed promising anti-icing ability by preventing ice/snow from adhering to the surface and delaying icing of water upon striking the surface. Furthermore, when our coating was applied onto a metal mesh, the resulting coated membrane was able to effectively separate dichloromethane (DCM), a nonpolar oil, from water. Combined with good thermal and adhesion properties, the existence of all the aforementioned properties makes the developed nanocomposite a very promising coating material for multifunctional application purposes.