Photolysis of perfluoroazooctane with diamond and related materials, such as diamond powders, films, diamond-like carbon (DLC) and nanodiamond films, led to a chemical modification of the surface to introduce perfluorooctyl functional groups, confirmed by means of FT-IR, XPS, Raman and TOF-SIMS measurements. The diamond and related materials modified with fluorine moieties showed an improvement of frictional property and a reduction of surface energy evaluated by contact angle to water, compared with pristine diamond, DLC and nanodiamond films. The results on the values of water contact angle depending on irradiation time are consistent with those of F/C ratio of fluorinated diamond and related materials by monitoring with XPS.