Oxidative electrochemical polymerization of (N,N'-ethylenebis(salicylideneaminato)) nickel(II), [Ni(salen)li in acetonitrile/TEAP was reinvestigated. The polymers were characterized by in situ FTIR and UV-visible spectroscopies in order to explore film structure and to clarify the electronic states as a function of the electrochemically controlled applied redox potential; oxidized species involved in polymerization and oxidative switching of the polymer were also assessed by en situ EPR experiments. Integration of data from all techniques revealed that (a) electropolymerization of [Ni(salen)] is ultimately a Ligand-based-process that takes place through a mixture of o- and p-linking of the phenyl rings and (b) poly[Ni(salen)] exhibits physical/chemical properties that cannot be attributed to an aggregation of individual complexes, behaving rather like a polyphenylene compound, with the metal ion acting as a bridge between biphenylene moieties.