Bottlebrush networks designed to be constitutional isomers of each other were synthesized for the first time. These network constitutional isomers (NCIs) have significantly different mechanical properties depending on their kinetic chain lengths ( R K ), which are controlled by the monomer-to-initiator ratio. Specifically, the low frequency moduli, yield behavior, elongation at break, and adhesive strength of these NCIs are different at the same cross-link densities. The NCI concept is extended to include R K s' dispersity through the choice of the catalyst. These NCIs highlight the impact of living polymerization chemistry on network formation. The use of living polymerization chemistry to synthesize new networks, including NCIs, is expected to significantly advance the development of next-generation materials.