A new surface modification technique is developed by taking advantage of unique stratification behaviors of amphiphilic Janus particles. Simply adding Janus particles to a conventional coating formulation can render a hydrophilic coating into hydrophobic surface, and drastically reduces the surface tackiness. Robust hydrophobic coatings with strong adhesion can be created using this method. In addition, the coating maintains its high water contact angle even after solvent rinsing, whereas conventional coating completely breaks down. These results suggest that Janus particles can be used as a novel additive to provide cost-effective and commercially scalable solutions to many long-standing challenges in waterborne emulsion coatings, including water resistance, adhesion, surface hardness and film formation. The study also opens new front for Janus particle research and provides a novel strategy to self-assemble and fabricate hierarchical structures. The results may open broad applications beyond coating materials, including cosmetics, adhesives, drug formulations and additive manufacturing.