The light-induced grafting reaction of acrylate monomers containing hindered piperidine groups (HALS) onto poly[bis(4-benzylphenoxy)phosphazene] is described as a function of several different experimental parameters, i.e., type of photoinitiator (benzophenone or benzoin ethyl ether), monomer concentration, solvent composition, light intensity, and swelling of the polyphosphazene films. The obtained phosphazene-g-HALS-containing acrylate-grafted copolymers, irradiated with light of wavelength longer than 300 nm under accelerated photooxidative conditions to test the photostabilizing ability of the grafted HALS groups, showed that the hindered piperidine groups grafted onto the polyphosphazene matrix are able to considerably depress she damage caused to the poly [bis(4-benzylphenoxy)phosphazene] films during light exposure. The efficiency of this process seems to be related to the amount of HALS residues grafted onto the phosphazene substrates.