Two methods for the addition of pendent dialkyl phosphonate units onto aryloxyphosphazenes, at both the polymeric and cyclic trimer levels, are described. Sodium organophosphites or halogenated organophosphates were used as the phosphonating agents and were allowed to react with bromomethylene- or lithio-functionalized aryloxyphosphazenes, respectively. Phosphonation of bromo-methylene-phenoxy side groups proceeded with similar to 100% conversion, while phosphonation via lithiophenoxy intermediates yielded 80-85% conversion. The presence of a direct phosphorus-carbon bond in all products was confirmed by C-13 NMR. Well-defined, cyclic trimers and polymers were obtained via both methods.