The title compound consists of the bulky 2,6-di-tert-butylphenoxy group and two phosphazene rings joined by a P-P bond [2.193 (2) angstrom]. The bulky group plays a predominant role in the distortion of the molecule as a whole. This distortion results in deviations of the benzene and phosphazene rings from planarity and twists the rings with respect to each other. In monocyclophosphazenes, the endocyclic angles about the P atom decrease while the exocyclic angles increase. This is in contrast to the behaviour of title compound (a bicyclophosphazene) in which the exo- and endocyclic angles about the P atoms both decrease on substitution.