Polymer complexes of nickel with SalEn-type li-gands (SalEn=N,N′-bis (salicylidene) ethylenediamine) pos-sess a number of unique properties, such as high redox con-ductivity, electrochromic behavior and selective catalytic ac-tivity in heterogeneous reactions. However, the mechanism oftheir redox transformation is still not clear. To understand thismechanism, we have performed a combined study of electro-chemical and spectral properties of polymers derived fromnickel complexes with various SalEn-type ligands containingmethoxy substituents in phenyl rings, and methyl substituentsin imino bridges. Experimental data were correlated with theresults of density functional theory (DFT) calculations formodel chains consisting of one to four monomer units. Wefound that, in acetonitrile-based supporting electrolyte, oxida-tion of such complexes, regardless of ligand substituents,proceeds via two routes, leading to formation of two oxidizedforms: for the first one, a good correlation between experi-mental and computatio