In this study, the chemical structure at the interfaces of nanocomposite thin films, consisting of MgF2 nanoparticles and a plasma polymer fluorocarbon (PPFC) matrix, was analyzed to elucidate the relationship between fluorine dispersion and surface properties. Using self‐made MgF2–carbon nanotube–polytetrafluoroethylene ternary composite sputtering targets, MgF2 nanoparticles were successfully embedded in the PPFC matrix through sputtering. The spectrometric analysis showed that the fluorine atoms transfer at the nanoparticle interface created a carbon‐rich region in the PPFC polymer matrix, resulting in higher thin film hardness. The optimized MgF2 nanoparticle/PPFC matrix thin film showed that surface hardness reached 4.32 GPa, and it also exhibited high optical transparency and water repellency. MgF2–PPFC nanocomposite thin film could be applicable to protective optical coatings for display and automotive windows.