2,6-Dibromo-4-(3′,5′-di-tert-butyl-4′-acetoxyphenyl)styrene was polymerized in a one-pot reaction using a palladium catalyst, and subsequent hydrolysis and oxidation yielded the hyperbranched poly[(4-(3′,5′-di-tert-butyl-4′-ylooxyphenyl)-1,2,(6)-phenylenevinylene)], which three-directionally satisfies both an alternant but non-Kekulé-type π-conjugation and the ferromagnetic connectivity of the unpaired electrons of the pendant phenoxyl. The AFM image, unusually low solution viscosity, and low chemical reactivity of the phenol group indicated the polymer to have a highly branched and globular structure. In spite of the extremely crowded branching, π-conjugation in the polymer skeleton was maintained, as indicated by photoelectron and EPR spectroscopies. The phenoxyl polymer even with a spin concentration of only 0.4 spin per monomer unit displayed an average S value of 3.