New dendritic poly(phenylazomethine)s (DPAs) with dodecyl end groups (C12DPA) have been synthesized. C12DPA showed stepwise radial complexation with metals as a metal‐storage nanocapsule. Through modification with dodecyl, the properties of environmental responsiveness and self‐assembly become apparent for C12DPA as a π‐conjugated soft material. The dodecyl‐modified DPAs (C12DPAG4) were synthesized up to the fourth generation dendrimer, for the first time, which is a nanocapsule with a basic atmosphere for metal complexes in a hydrophobic environment. In addition, we found a suitable structure and conditions for the fibrous self‐assembly of DPA through the precise design of its dendritic structure. C12DPA, with an asymmetric structure, showed a fibrous assembly by a solvent drop‐casting. The metal‐complexed C12DPA showed an assembly different from the fibrous one through metal complexation on DPA imines. Interestingly, the vesicular assembly structure of C12DPA has been observed by the complexation of CuCl2 in toluene. In this study, we investigated the unique properties of C12DPA as a novel π‐conjugated soft material.