A convergent approach for the incorporation of arylphosphonate moieties into the cyclotriphosphazene unit is described. The synthesis is based on the reaction of hexachlorocyclotriphosphazene with diethyl 4-hydroxyphenylphosphonate in the presence of anhydrous potassium carbonate. This reaction is characterised by substitution of the chloride atoms, which thus produces the hexaarylphosphono derivative