Hydrophobic coatings have considerable potential applications in many fields. Ease of operation and high durability are essential for practical use. Fast curing and being solvent-free are a plus, and if they possess certain characteristics (antigraffiti, good adhesion, high hardness, heat resistance, wide range of applicability, etc.) at the same time, it is a dream solution. Herein, a facile one-step approach with the above features was reported for a UV curable robust hydrophobic coating based on Epoxy Polyhedral Oligomeric Silsesquioxanes (EP-POSSs). The structure and surface morphology of these EP-POSSs and their derivatives were systematically studied. Because of the core-in-cage structure which was constructed by repeating units of R-Si(O 1/2 ) 3 and the strong covalent bonds of Si–C and Si–O, the coatings displayed high pencil hardness (6–8H), high thermal stability with initial decomposition temperature around 350–400 °C, and a high water contact angle (up to 108.06°) even after outdoor exposure for a month. These POSSs and their derivatives are expected to find uses in various applications such as stain resistance, self-cleaning, scratch resistance, and cigarette moxibustion resistance of wood furniture, kitchenware, and medical and industrial appliances.