Hybrid inorganic/organic polymers have been prepared by copolymerizing a silanol terminated polydimethylsiloxane (PDMS) with an Octa(aminophenyl) -silsesquioxane (POSS). The AO resistance of these POSS/PDMS hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces have been characterized by X-ray photoelectron spectroscopy. The XPS data indicate that the carbon content of the near-surface region is decreased from 65.3 to 18.9 at% after AO exposure. The oxygen and silicon concentrations in the near-surface region increase after AO exposure. The data reveal the formation of a passive inorganic SiO2 layer on the POSS/PDMS hybrid films during the AO exposure, which serves as a protective barrier preventing further degradation of the underlying polymer with increased exposure to the AO flux. The erosion yield of the POSS/PDMS (20 wt%) hybrid film was 1.7×10-26 cm3/atom, decreased by two orders of magnitude compared with the value of 3.0×10-24 cm3/atom of the polyimide film.